diff --git a/lib/scope.js b/lib/scope.js
index 359c4f97da3..3e18b6d3fd4 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -178,6 +178,13 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
             });
             return true;
         }
+        if (node instanceof AST_Switch) {
+            node.expression.walk(tw);
+            walk_scope(function() {
+                walk_body(node, tw);
+            });
+            return true;
+        }
         if (node instanceof AST_SwitchBranch) {
             node.init_vars(scope);
             descend();
diff --git a/test/compress/const.js b/test/compress/const.js
index 8c56980fe17..df948ac4d9e 100644
--- a/test/compress/const.js
+++ b/test/compress/const.js
@@ -2204,3 +2204,30 @@ issue_5660: {
     }
     expect_stdout: true
 }
+
+issue_5787: {
+    options = {
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            const a = 42;
+            switch (a) {
+              case 42:
+                const a = "PASS";
+                return a;
+            }
+        }());
+    }
+    expect: {
+        console.log(function() {
+            const a = 42;
+            switch (a) {
+              case 42:
+                const a = "PASS";
+                return a;
+            }
+        }());
+    }
+    expect_stdout: true
+}
diff --git a/test/compress/let.js b/test/compress/let.js
index ba6c4bc74ae..44c58431bf3 100644
--- a/test/compress/let.js
+++ b/test/compress/let.js
@@ -2537,3 +2537,33 @@ issue_5759: {
     ]
     node_version: ">=4"
 }
+
+issue_5787: {
+    options = {
+        unused: true,
+    }
+    input: {
+        "use strict";
+        console.log(function() {
+            let a = 42;
+            switch (a) {
+              case 42:
+                let a = "PASS";
+                return a;
+            }
+        }());
+    }
+    expect: {
+        "use strict";
+        console.log(function() {
+            let a = 42;
+            switch (a) {
+              case 42:
+                let a = "PASS";
+                return a;
+            }
+        }());
+    }
+    expect_stdout: true
+    node_version: ">=4"
+}
diff --git a/test/compress/rename.js b/test/compress/rename.js
index 1d553f060b0..2f68b505f5b 100644
--- a/test/compress/rename.js
+++ b/test/compress/rename.js
@@ -739,3 +739,56 @@ issue_3480_ie8_toplevel: {
     }
     expect_stdout: "PASS"
 }
+
+issue_5787_1: {
+    rename = true
+    input: {
+        console.log(function() {
+            const a = 42;
+            switch (a) {
+              case 42:
+                const a = "PASS";
+                return a;
+            }
+        }());
+    }
+    expect: {
+        console.log(function() {
+            const a = 42;
+            switch (a) {
+              case 42:
+                const a = "PASS";
+                return a;
+            }
+        }());
+    }
+    expect_stdout: true
+}
+
+issue_5787_2: {
+    rename = true
+    input: {
+        "use strict";
+        console.log(function() {
+            let a = 42;
+            switch (a) {
+              case 42:
+                let a = "PASS";
+                return a;
+            }
+        }());
+    }
+    expect: {
+        "use strict";
+        console.log(function() {
+            let a = 42;
+            switch (a) {
+              case 42:
+                let b = "PASS";
+                return b;
+            }
+        }());
+    }
+    expect_stdout: true
+    node_version: ">=4"
+}