diff --git a/src/libdredd/src/mutation_replace_expr.cc b/src/libdredd/src/mutation_replace_expr.cc
index 79f358e2..32d18c42 100644
--- a/src/libdredd/src/mutation_replace_expr.cc
+++ b/src/libdredd/src/mutation_replace_expr.cc
@@ -538,18 +538,18 @@ void MutationReplaceExpr::ReplaceExprWithFunctionCall(
     suffix.append("; }");
   }
 
-  if (!ast_context.getLangOpts().CPlusPlus) {
-    if (expr_->isLValue() && input_type.ends_with('*')) {
-      prefix.append("&(");
-      suffix.append(")");
-    } else if (const auto* binary_expr =
-                   llvm::dyn_cast<clang::BinaryOperator>(expr_)) {
-      // The comma operator requires special care in C, to avoid it appearing to
-      // provide multiple parameters for an enclosing function call.
-      if (binary_expr->isCommaOp()) {
-        prefix.append("(");
-        suffix.append(")");
-      }
+  if (!ast_context.getLangOpts().CPlusPlus && expr_->isLValue() &&
+      input_type.ends_with('*')) {
+    prefix.append("&(");
+    suffix = ")" + suffix;
+  }
+
+  if (const auto* binary_expr = llvm::dyn_cast<clang::BinaryOperator>(expr_)) {
+    // The comma operator requires special care to avoid it appearing to
+    // provide multiple parameters for an enclosing function call.
+    if (binary_expr->isCommaOp()) {
+      prefix.append("(");
+      suffix = ")" + suffix;
     }
   }
 
diff --git a/test/single_file/comma_initialization.c b/test/single_file/comma_initialization.c
new file mode 100644
index 00000000..9843f02a
--- /dev/null
+++ b/test/single_file/comma_initialization.c
@@ -0,0 +1,3 @@
+int main() {
+ int x = (1,0);
+}
diff --git a/test/single_file/comma_initialization.c.expected b/test/single_file/comma_initialization.c.expected
new file mode 100644
index 00000000..4ebe758b
--- /dev/null
+++ b/test/single_file/comma_initialization.c.expected
@@ -0,0 +1,60 @@
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifdef _MSC_VER
+#define thread_local __declspec(thread)
+#elif __APPLE__
+#define thread_local __thread
+#else
+#include <threads.h>
+#endif
+
+static thread_local int __dredd_some_mutation_enabled = 1;
+static int __dredd_enabled_mutation(int local_mutation_id) {
+  static thread_local int initialized = 0;
+  static thread_local uint64_t enabled_bitset[1];
+  if (!initialized) {
+    int some_mutation_enabled = 0;
+    const char* dredd_environment_variable = getenv("DREDD_ENABLED_MUTATION");
+    if (dredd_environment_variable) {
+      char* temp = malloc(strlen(dredd_environment_variable) + 1);
+      strcpy(temp, dredd_environment_variable);
+      char* token;
+      token = strtok(temp, ",");
+      while(token) {
+        int value = atoi(token);
+        int local_value = value - 0;
+        if (local_value >= 0 && local_value < 7) {
+          enabled_bitset[local_value / 64] |= (1 << (local_value % 64));
+          some_mutation_enabled = 1;
+        }
+        token = strtok(NULL, ",");
+      }
+      free(temp);
+    }
+    initialized = 1;
+    __dredd_some_mutation_enabled = some_mutation_enabled;
+  }
+  return enabled_bitset[local_mutation_id / 64] & (1 << (local_mutation_id % 64));
+}
+
+static int __dredd_replace_expr_int_zero(int arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return 1;
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return -1;
+  return arg;
+}
+
+static int __dredd_replace_expr_int_one(int arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return ~(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return 0;
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return -1;
+  return arg;
+}
+
+int main() {
+ int x = (__dredd_replace_expr_int_zero((__dredd_replace_expr_int_one(1, 0),__dredd_replace_expr_int_zero(0, 3)), 5));
+}
diff --git a/test/single_file/comma_initialization.c.noopt.expected b/test/single_file/comma_initialization.c.noopt.expected
new file mode 100644
index 00000000..e16fe37e
--- /dev/null
+++ b/test/single_file/comma_initialization.c.noopt.expected
@@ -0,0 +1,56 @@
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifdef _MSC_VER
+#define thread_local __declspec(thread)
+#elif __APPLE__
+#define thread_local __thread
+#else
+#include <threads.h>
+#endif
+
+static thread_local int __dredd_some_mutation_enabled = 1;
+static int __dredd_enabled_mutation(int local_mutation_id) {
+  static thread_local int initialized = 0;
+  static thread_local uint64_t enabled_bitset[1];
+  if (!initialized) {
+    int some_mutation_enabled = 0;
+    const char* dredd_environment_variable = getenv("DREDD_ENABLED_MUTATION");
+    if (dredd_environment_variable) {
+      char* temp = malloc(strlen(dredd_environment_variable) + 1);
+      strcpy(temp, dredd_environment_variable);
+      char* token;
+      token = strtok(temp, ",");
+      while(token) {
+        int value = atoi(token);
+        int local_value = value - 0;
+        if (local_value >= 0 && local_value < 24) {
+          enabled_bitset[local_value / 64] |= (1 << (local_value % 64));
+          some_mutation_enabled = 1;
+        }
+        token = strtok(NULL, ",");
+      }
+      free(temp);
+    }
+    initialized = 1;
+    __dredd_some_mutation_enabled = some_mutation_enabled;
+  }
+  return enabled_bitset[local_mutation_id / 64] & (1 << (local_mutation_id % 64));
+}
+
+static int __dredd_replace_expr_int(int arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return !(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return ~(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return -(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return 0;
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return 1;
+  if (__dredd_enabled_mutation(local_mutation_id + 5)) return -1;
+  return arg;
+}
+
+int main() {
+ int x = __dredd_replace_expr_int((__dredd_replace_expr_int((__dredd_replace_expr_int(1, 0),__dredd_replace_expr_int(0, 6)), 12)), 18);
+}
diff --git a/test/single_file/comma_initialization.cc b/test/single_file/comma_initialization.cc
new file mode 100644
index 00000000..37226a11
--- /dev/null
+++ b/test/single_file/comma_initialization.cc
@@ -0,0 +1,3 @@
+int main() {
+  int b((1,0));
+}
diff --git a/test/single_file/comma_initialization.cc.expected b/test/single_file/comma_initialization.cc.expected
new file mode 100644
index 00000000..56c094e8
--- /dev/null
+++ b/test/single_file/comma_initialization.cc.expected
@@ -0,0 +1,62 @@
+#include <cinttypes>
+#include <cstddef>
+#include <functional>
+#include <string>
+
+
+#ifdef _MSC_VER
+#define thread_local __declspec(thread)
+#elif __APPLE__
+#define thread_local __thread
+#endif
+
+static thread_local bool __dredd_some_mutation_enabled = true;
+static bool __dredd_enabled_mutation(int local_mutation_id) {
+  static thread_local bool initialized = false;
+  static thread_local uint64_t enabled_bitset[1];
+  if (!initialized) {
+    bool some_mutation_enabled = false;
+    const char* dredd_environment_variable = std::getenv("DREDD_ENABLED_MUTATION");
+    if (dredd_environment_variable != nullptr) {
+      std::string contents(dredd_environment_variable);
+      while (true) {
+        size_t pos = contents.find(",");
+        std::string token = (pos == std::string::npos ? contents : contents.substr(0, pos));
+        if (!token.empty()) {
+          int value = std::stoi(token);
+          int local_value = value - 0;
+          if (local_value >= 0 && local_value < 7) {
+            enabled_bitset[local_value / 64] |= (1 << (local_value % 64));
+            some_mutation_enabled = true;
+          }
+        }
+        if (pos == std::string::npos) {
+          break;
+        }
+        contents.erase(0, pos + 1);
+      }
+    }
+    initialized = true;
+    __dredd_some_mutation_enabled = some_mutation_enabled;
+  }
+  return (enabled_bitset[local_mutation_id / 64] & (1 << (local_mutation_id % 64))) != 0;
+}
+
+static int __dredd_replace_expr_int_zero(int arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return 1;
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return -1;
+  return arg;
+}
+
+static int __dredd_replace_expr_int_one(int arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return ~(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return 0;
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return -1;
+  return arg;
+}
+
+int main() {
+  int b((__dredd_replace_expr_int_zero((__dredd_replace_expr_int_one(1, 0),__dredd_replace_expr_int_zero(0, 3)), 5)));
+}
diff --git a/test/single_file/comma_initialization.cc.noopt.expected b/test/single_file/comma_initialization.cc.noopt.expected
new file mode 100644
index 00000000..350d23cb
--- /dev/null
+++ b/test/single_file/comma_initialization.cc.noopt.expected
@@ -0,0 +1,58 @@
+#include <cinttypes>
+#include <cstddef>
+#include <functional>
+#include <string>
+
+
+#ifdef _MSC_VER
+#define thread_local __declspec(thread)
+#elif __APPLE__
+#define thread_local __thread
+#endif
+
+static thread_local bool __dredd_some_mutation_enabled = true;
+static bool __dredd_enabled_mutation(int local_mutation_id) {
+  static thread_local bool initialized = false;
+  static thread_local uint64_t enabled_bitset[1];
+  if (!initialized) {
+    bool some_mutation_enabled = false;
+    const char* dredd_environment_variable = std::getenv("DREDD_ENABLED_MUTATION");
+    if (dredd_environment_variable != nullptr) {
+      std::string contents(dredd_environment_variable);
+      while (true) {
+        size_t pos = contents.find(",");
+        std::string token = (pos == std::string::npos ? contents : contents.substr(0, pos));
+        if (!token.empty()) {
+          int value = std::stoi(token);
+          int local_value = value - 0;
+          if (local_value >= 0 && local_value < 24) {
+            enabled_bitset[local_value / 64] |= (1 << (local_value % 64));
+            some_mutation_enabled = true;
+          }
+        }
+        if (pos == std::string::npos) {
+          break;
+        }
+        contents.erase(0, pos + 1);
+      }
+    }
+    initialized = true;
+    __dredd_some_mutation_enabled = some_mutation_enabled;
+  }
+  return (enabled_bitset[local_mutation_id / 64] & (1 << (local_mutation_id % 64))) != 0;
+}
+
+static int __dredd_replace_expr_int(int arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return !(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return ~(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return -(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return 0;
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return 1;
+  if (__dredd_enabled_mutation(local_mutation_id + 5)) return -1;
+  return arg;
+}
+
+int main() {
+  int b(__dredd_replace_expr_int((__dredd_replace_expr_int((__dredd_replace_expr_int(1, 0),__dredd_replace_expr_int(0, 6)), 12)), 18));
+}
diff --git a/test/single_file/comma_side_effects.c b/test/single_file/comma_side_effects.c
new file mode 100644
index 00000000..56cbc44c
--- /dev/null
+++ b/test/single_file/comma_side_effects.c
@@ -0,0 +1,4 @@
+int main() {
+  int x = 0;
+  x = (0, x++);
+}
diff --git a/test/single_file/comma_side_effects.c.expected b/test/single_file/comma_side_effects.c.expected
new file mode 100644
index 00000000..62b43b77
--- /dev/null
+++ b/test/single_file/comma_side_effects.c.expected
@@ -0,0 +1,89 @@
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifdef _MSC_VER
+#define thread_local __declspec(thread)
+#elif __APPLE__
+#define thread_local __thread
+#else
+#include <threads.h>
+#endif
+
+static thread_local int __dredd_some_mutation_enabled = 1;
+static int __dredd_enabled_mutation(int local_mutation_id) {
+  static thread_local int initialized = 0;
+  static thread_local uint64_t enabled_bitset[1];
+  if (!initialized) {
+    int some_mutation_enabled = 0;
+    const char* dredd_environment_variable = getenv("DREDD_ENABLED_MUTATION");
+    if (dredd_environment_variable) {
+      char* temp = malloc(strlen(dredd_environment_variable) + 1);
+      strcpy(temp, dredd_environment_variable);
+      char* token;
+      token = strtok(temp, ",");
+      while(token) {
+        int value = atoi(token);
+        int local_value = value - 0;
+        if (local_value >= 0 && local_value < 32) {
+          enabled_bitset[local_value / 64] |= (1 << (local_value % 64));
+          some_mutation_enabled = 1;
+        }
+        token = strtok(NULL, ",");
+      }
+      free(temp);
+    }
+    initialized = 1;
+    __dredd_some_mutation_enabled = some_mutation_enabled;
+  }
+  return enabled_bitset[local_mutation_id / 64] & (1 << (local_mutation_id % 64));
+}
+
+static int __dredd_replace_unary_operator_PostInc_int(int* arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return (*arg)++;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return (*arg)--;
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return ~(*arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return -(*arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return !(*arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return (*arg);
+  return (*arg)++;
+}
+
+static int __dredd_replace_expr_int_zero(int arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return 1;
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return -1;
+  return arg;
+}
+
+static int __dredd_replace_expr_int(int arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return !(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return ~(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return -(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return 0;
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return 1;
+  if (__dredd_enabled_mutation(local_mutation_id + 5)) return -1;
+  return arg;
+}
+
+static int __dredd_replace_binary_operator_Assign_arg1_int_arg2_int(int* arg1, int arg2, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return (*arg1) = arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return (*arg1) += arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return (*arg1) &= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return (*arg1) /= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return (*arg1) *= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return (*arg1) |= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 5)) return (*arg1) %= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 6)) return (*arg1) <<= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 7)) return (*arg1) >>= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 8)) return (*arg1) -= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 9)) return (*arg1) ^= arg2;
+  return (*arg1) = arg2;
+}
+
+int main() {
+  int x = __dredd_replace_expr_int_zero(0, 0);
+  if (!__dredd_enabled_mutation(31)) { __dredd_replace_binary_operator_Assign_arg1_int_arg2_int(&(x) , (__dredd_replace_expr_int((__dredd_replace_expr_int_zero(0, 2), __dredd_replace_expr_int(__dredd_replace_unary_operator_PostInc_int(&(x), 4), 9)), 15)), 21); }
+}
diff --git a/test/single_file/comma_side_effects.c.noopt.expected b/test/single_file/comma_side_effects.c.noopt.expected
new file mode 100644
index 00000000..ec6b399f
--- /dev/null
+++ b/test/single_file/comma_side_effects.c.noopt.expected
@@ -0,0 +1,82 @@
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifdef _MSC_VER
+#define thread_local __declspec(thread)
+#elif __APPLE__
+#define thread_local __thread
+#else
+#include <threads.h>
+#endif
+
+static thread_local int __dredd_some_mutation_enabled = 1;
+static int __dredd_enabled_mutation(int local_mutation_id) {
+  static thread_local int initialized = 0;
+  static thread_local uint64_t enabled_bitset[1];
+  if (!initialized) {
+    int some_mutation_enabled = 0;
+    const char* dredd_environment_variable = getenv("DREDD_ENABLED_MUTATION");
+    if (dredd_environment_variable) {
+      char* temp = malloc(strlen(dredd_environment_variable) + 1);
+      strcpy(temp, dredd_environment_variable);
+      char* token;
+      token = strtok(temp, ",");
+      while(token) {
+        int value = atoi(token);
+        int local_value = value - 0;
+        if (local_value >= 0 && local_value < 52) {
+          enabled_bitset[local_value / 64] |= (1 << (local_value % 64));
+          some_mutation_enabled = 1;
+        }
+        token = strtok(NULL, ",");
+      }
+      free(temp);
+    }
+    initialized = 1;
+    __dredd_some_mutation_enabled = some_mutation_enabled;
+  }
+  return enabled_bitset[local_mutation_id / 64] & (1 << (local_mutation_id % 64));
+}
+
+static int __dredd_replace_unary_operator_PostInc_int(int* arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return (*arg)++;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return (*arg)--;
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return ~(*arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return -(*arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return !(*arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return (*arg);
+  return (*arg)++;
+}
+
+static int __dredd_replace_expr_int(int arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return !(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return ~(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return -(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return 0;
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return 1;
+  if (__dredd_enabled_mutation(local_mutation_id + 5)) return -1;
+  return arg;
+}
+
+static int __dredd_replace_binary_operator_Assign_arg1_int_arg2_int(int* arg1, int arg2, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return (*arg1) = arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return (*arg1) += arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return (*arg1) &= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return (*arg1) /= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return (*arg1) *= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return (*arg1) |= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 5)) return (*arg1) %= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 6)) return (*arg1) <<= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 7)) return (*arg1) >>= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 8)) return (*arg1) -= arg2;
+  if (__dredd_enabled_mutation(local_mutation_id + 9)) return (*arg1) ^= arg2;
+  return (*arg1) = arg2;
+}
+
+int main() {
+  int x = __dredd_replace_expr_int(0, 0);
+  if (!__dredd_enabled_mutation(51)) { __dredd_replace_expr_int(__dredd_replace_binary_operator_Assign_arg1_int_arg2_int(&(x) , __dredd_replace_expr_int((__dredd_replace_expr_int((__dredd_replace_expr_int(0, 6), __dredd_replace_expr_int(__dredd_replace_unary_operator_PostInc_int(&(x), 12), 17)), 23)), 29), 35), 45); }
+}
diff --git a/test/single_file/comma_side_effects.cc b/test/single_file/comma_side_effects.cc
new file mode 100644
index 00000000..56cbc44c
--- /dev/null
+++ b/test/single_file/comma_side_effects.cc
@@ -0,0 +1,4 @@
+int main() {
+  int x = 0;
+  x = (0, x++);
+}
diff --git a/test/single_file/comma_side_effects.cc.expected b/test/single_file/comma_side_effects.cc.expected
new file mode 100644
index 00000000..cbd5db97
--- /dev/null
+++ b/test/single_file/comma_side_effects.cc.expected
@@ -0,0 +1,91 @@
+#include <cinttypes>
+#include <cstddef>
+#include <functional>
+#include <string>
+
+
+#ifdef _MSC_VER
+#define thread_local __declspec(thread)
+#elif __APPLE__
+#define thread_local __thread
+#endif
+
+static thread_local bool __dredd_some_mutation_enabled = true;
+static bool __dredd_enabled_mutation(int local_mutation_id) {
+  static thread_local bool initialized = false;
+  static thread_local uint64_t enabled_bitset[1];
+  if (!initialized) {
+    bool some_mutation_enabled = false;
+    const char* dredd_environment_variable = std::getenv("DREDD_ENABLED_MUTATION");
+    if (dredd_environment_variable != nullptr) {
+      std::string contents(dredd_environment_variable);
+      while (true) {
+        size_t pos = contents.find(",");
+        std::string token = (pos == std::string::npos ? contents : contents.substr(0, pos));
+        if (!token.empty()) {
+          int value = std::stoi(token);
+          int local_value = value - 0;
+          if (local_value >= 0 && local_value < 32) {
+            enabled_bitset[local_value / 64] |= (1 << (local_value % 64));
+            some_mutation_enabled = true;
+          }
+        }
+        if (pos == std::string::npos) {
+          break;
+        }
+        contents.erase(0, pos + 1);
+      }
+    }
+    initialized = true;
+    __dredd_some_mutation_enabled = some_mutation_enabled;
+  }
+  return (enabled_bitset[local_mutation_id / 64] & (1 << (local_mutation_id % 64))) != 0;
+}
+
+static int& __dredd_replace_binary_operator_Assign_arg1_int_arg2_int(int& arg1, std::function<int()> arg2, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg1 = arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return arg1 += arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return arg1 &= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return arg1 /= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return arg1 *= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return arg1 |= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 5)) return arg1 %= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 6)) return arg1 <<= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 7)) return arg1 >>= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 8)) return arg1 -= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 9)) return arg1 ^= arg2();
+  return arg1 = arg2();
+}
+
+static int __dredd_replace_unary_operator_PostInc_int(std::function<int&()> arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg()++;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return arg()--;
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return ~arg();
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return -arg();
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return !arg();
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return arg();
+  return arg()++;
+}
+
+static int __dredd_replace_expr_int_zero(int arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return 1;
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return -1;
+  return arg;
+}
+
+static int __dredd_replace_expr_int(std::function<int()> arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg();
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return !(arg());
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return ~(arg());
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return -(arg());
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return 0;
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return 1;
+  if (__dredd_enabled_mutation(local_mutation_id + 5)) return -1;
+  return arg();
+}
+
+int main() {
+  int x = __dredd_replace_expr_int_zero(0, 0);
+  if (!__dredd_enabled_mutation(31)) { __dredd_replace_binary_operator_Assign_arg1_int_arg2_int(x , [&]() -> int { return static_cast<int>((__dredd_replace_expr_int([&]() -> int { return static_cast<int>((__dredd_replace_expr_int_zero(0, 2), __dredd_replace_expr_int([&]() -> int { return static_cast<int>(__dredd_replace_unary_operator_PostInc_int([&]() -> int& { return static_cast<int&>(x); }, 4)); }, 9))); }, 15))); }, 21); }
+}
diff --git a/test/single_file/comma_side_effects.cc.noopt.expected b/test/single_file/comma_side_effects.cc.noopt.expected
new file mode 100644
index 00000000..4fe5c605
--- /dev/null
+++ b/test/single_file/comma_side_effects.cc.noopt.expected
@@ -0,0 +1,95 @@
+#include <cinttypes>
+#include <cstddef>
+#include <functional>
+#include <string>
+
+
+#ifdef _MSC_VER
+#define thread_local __declspec(thread)
+#elif __APPLE__
+#define thread_local __thread
+#endif
+
+static thread_local bool __dredd_some_mutation_enabled = true;
+static bool __dredd_enabled_mutation(int local_mutation_id) {
+  static thread_local bool initialized = false;
+  static thread_local uint64_t enabled_bitset[1];
+  if (!initialized) {
+    bool some_mutation_enabled = false;
+    const char* dredd_environment_variable = std::getenv("DREDD_ENABLED_MUTATION");
+    if (dredd_environment_variable != nullptr) {
+      std::string contents(dredd_environment_variable);
+      while (true) {
+        size_t pos = contents.find(",");
+        std::string token = (pos == std::string::npos ? contents : contents.substr(0, pos));
+        if (!token.empty()) {
+          int value = std::stoi(token);
+          int local_value = value - 0;
+          if (local_value >= 0 && local_value < 46) {
+            enabled_bitset[local_value / 64] |= (1 << (local_value % 64));
+            some_mutation_enabled = true;
+          }
+        }
+        if (pos == std::string::npos) {
+          break;
+        }
+        contents.erase(0, pos + 1);
+      }
+    }
+    initialized = true;
+    __dredd_some_mutation_enabled = some_mutation_enabled;
+  }
+  return (enabled_bitset[local_mutation_id / 64] & (1 << (local_mutation_id % 64))) != 0;
+}
+
+static int& __dredd_replace_binary_operator_Assign_arg1_int_arg2_int(int& arg1, std::function<int()> arg2, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg1 = arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return arg1 += arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return arg1 &= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return arg1 /= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return arg1 *= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return arg1 |= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 5)) return arg1 %= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 6)) return arg1 <<= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 7)) return arg1 >>= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 8)) return arg1 -= arg2();
+  if (__dredd_enabled_mutation(local_mutation_id + 9)) return arg1 ^= arg2();
+  return arg1 = arg2();
+}
+
+static int __dredd_replace_unary_operator_PostInc_int(std::function<int&()> arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg()++;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return arg()--;
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return ~arg();
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return -arg();
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return !arg();
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return arg();
+  return arg()++;
+}
+
+static int __dredd_replace_expr_int(std::function<int()> arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg();
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return !(arg());
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return ~(arg());
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return -(arg());
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return 0;
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return 1;
+  if (__dredd_enabled_mutation(local_mutation_id + 5)) return -1;
+  return arg();
+}
+
+static int __dredd_replace_expr_int(int arg, int local_mutation_id) {
+  if (!__dredd_some_mutation_enabled) return arg;
+  if (__dredd_enabled_mutation(local_mutation_id + 0)) return !(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 1)) return ~(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 2)) return -(arg);
+  if (__dredd_enabled_mutation(local_mutation_id + 3)) return 0;
+  if (__dredd_enabled_mutation(local_mutation_id + 4)) return 1;
+  if (__dredd_enabled_mutation(local_mutation_id + 5)) return -1;
+  return arg;
+}
+
+int main() {
+  int x = __dredd_replace_expr_int(0, 0);
+  if (!__dredd_enabled_mutation(45)) { __dredd_replace_binary_operator_Assign_arg1_int_arg2_int(x , [&]() -> int { return static_cast<int>(__dredd_replace_expr_int([&]() -> int { return static_cast<int>((__dredd_replace_expr_int([&]() -> int { return static_cast<int>((__dredd_replace_expr_int(0, 6), __dredd_replace_expr_int([&]() -> int { return static_cast<int>(__dredd_replace_unary_operator_PostInc_int([&]() -> int& { return static_cast<int&>(x); }, 12)); }, 17))); }, 23))); }, 29)); }, 35); }
+}