diff --git a/src/main/java/com/google/devtools/build/lib/actions/ActionEnvironment.java b/src/main/java/com/google/devtools/build/lib/actions/ActionEnvironment.java
index 11def1f91b5b9a..2ac661cd711587 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/ActionEnvironment.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/ActionEnvironment.java
@@ -83,8 +83,8 @@ static class CompoundEnvironmentVariables implements EnvironmentVariables {
 
     static EnvironmentVariables create(
         Map<String, String> fixedVars, Set<String> inheritedVars, EnvironmentVariables base) {
-      if (fixedVars.isEmpty() && inheritedVars.isEmpty() && base.isEmpty()) {
-        return EMPTY_ENVIRONMENT_VARIABLES;
+      if (fixedVars.isEmpty() && inheritedVars.isEmpty()) {
+        return base;
       }
       return new CompoundEnvironmentVariables(fixedVars, inheritedVars, base);
     }
@@ -219,18 +219,22 @@ public static ActionEnvironment create(Map<String, String> fixedEnv) {
    * Returns a copy of the environment with the given fixed variables added to it, <em>overwriting
    * any existing occurrences of those variables</em>.
    */
-  public ActionEnvironment addFixedVariables(Map<String, String> fixedVars) {
-    return ActionEnvironment.create(
-        CompoundEnvironmentVariables.create(fixedVars, ImmutableSet.of(), vars));
+  public ActionEnvironment withAdditionalFixedVariables(Map<String, String> fixedVars) {
+    return withAdditionalVariables(fixedVars, ImmutableSet.of());
   }
 
   /**
    * Returns a copy of the environment with the given fixed and inherited variables added to it,
    * <em>overwriting any existing occurrences of those variables</em>.
    */
-  public ActionEnvironment addVariables(Map<String, String> fixedVars, Set<String> inheritedVars) {
-    return ActionEnvironment.create(
-        CompoundEnvironmentVariables.create(fixedVars, inheritedVars, vars));
+  public ActionEnvironment withAdditionalVariables(
+      Map<String, String> fixedVars, Set<String> inheritedVars) {
+    EnvironmentVariables newVars =
+        CompoundEnvironmentVariables.create(fixedVars, inheritedVars, vars);
+    if (newVars == vars) {
+      return this;
+    }
+    return ActionEnvironment.create(newVars);
   }
 
   /**
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/test/TestActionBuilder.java b/src/main/java/com/google/devtools/build/lib/analysis/test/TestActionBuilder.java
index 5825c2ab70b3fa..d7cb43efcd787b 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/test/TestActionBuilder.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/test/TestActionBuilder.java
@@ -413,7 +413,7 @@ private TestParams createTestAction(int shards)
                 testProperties,
                 runfilesSupport
                     .getActionEnvironment()
-                    .addVariables(extraTestEnv, extraInheritedEnv),
+                    .withAdditionalVariables(extraTestEnv, extraInheritedEnv),
                 executionSettings,
                 shard,
                 run,
diff --git a/src/main/java/com/google/devtools/build/lib/rules/java/JavaCompileActionBuilder.java b/src/main/java/com/google/devtools/build/lib/rules/java/JavaCompileActionBuilder.java
index 214cc1060c7b8e..5aa6094071e305 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/java/JavaCompileActionBuilder.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/java/JavaCompileActionBuilder.java
@@ -205,7 +205,10 @@ public JavaCompileAction build() {
     toolsBuilder.addTransitive(toolsJars);
 
     ActionEnvironment actionEnvironment =
-        ruleContext.getConfiguration().getActionEnvironment().addFixedVariables(UTF8_ENVIRONMENT);
+        ruleContext
+            .getConfiguration()
+            .getActionEnvironment()
+            .withAdditionalFixedVariables(UTF8_ENVIRONMENT);
 
     NestedSetBuilder<Artifact> mandatoryInputsBuilder = NestedSetBuilder.stableOrder();
     mandatoryInputsBuilder
diff --git a/src/main/java/com/google/devtools/build/lib/rules/java/JavaHeaderCompileActionBuilder.java b/src/main/java/com/google/devtools/build/lib/rules/java/JavaHeaderCompileActionBuilder.java
index 0838f8667e1c75..d36f3bd2a9e186 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/java/JavaHeaderCompileActionBuilder.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/java/JavaHeaderCompileActionBuilder.java
@@ -296,7 +296,10 @@ public void build(JavaToolchainProvider javaToolchain) throws InterruptedExcepti
     }
 
     ActionEnvironment actionEnvironment =
-        ruleContext.getConfiguration().getActionEnvironment().addFixedVariables(UTF8_ENVIRONMENT);
+        ruleContext
+            .getConfiguration()
+            .getActionEnvironment()
+            .withAdditionalFixedVariables(UTF8_ENVIRONMENT);
 
     OnDemandString progressMessage =
         new ProgressMessage(
diff --git a/src/test/java/com/google/devtools/build/lib/actions/ActionEnvironmentTest.java b/src/test/java/com/google/devtools/build/lib/actions/ActionEnvironmentTest.java
index 54119fc4da7332..8ff56fbc18f40d 100644
--- a/src/test/java/com/google/devtools/build/lib/actions/ActionEnvironmentTest.java
+++ b/src/test/java/com/google/devtools/build/lib/actions/ActionEnvironmentTest.java
@@ -34,7 +34,7 @@ public void compoundEnvOrdering() {
         ActionEnvironment.create(
             ImmutableMap.of("FOO", "foo1", "BAR", "bar"), ImmutableSet.of("baz"));
     // entries added by env2 override the existing entries
-    ActionEnvironment env2 = env1.addFixedVariables(ImmutableMap.of("FOO", "foo2"));
+    ActionEnvironment env2 = env1.withAdditionalFixedVariables(ImmutableMap.of("FOO", "foo2"));
 
     assertThat(env1.getFixedEnv()).containsExactly("FOO", "foo1", "BAR", "bar");
     assertThat(env1.getInheritedEnv()).containsExactly("baz");
@@ -48,7 +48,7 @@ public void fixedInheritedInteraction() {
     ActionEnvironment env =
         ActionEnvironment.create(
                 ImmutableMap.of("FIXED_ONLY", "fixed"), ImmutableSet.of("INHERITED_ONLY"))
-            .addVariables(
+            .withAdditionalVariables(
                 ImmutableMap.of("FIXED_AND_INHERITED", "fixed"),
                 ImmutableSet.of("FIXED_AND_INHERITED"));
     Map<String, String> clientEnv =
@@ -65,4 +65,17 @@ public void fixedInheritedInteraction() {
             "INHERITED_ONLY",
             "inherited");
   }
+
+  @Test
+  public void emptyEnvironmentInterning() {
+    ActionEnvironment emptyEnvironment =
+        ActionEnvironment.create(ImmutableMap.of(), ImmutableSet.of());
+    assertThat(emptyEnvironment).isSameInstanceAs(ActionEnvironment.EMPTY);
+
+    ActionEnvironment base =
+        ActionEnvironment.create(ImmutableMap.of("FOO", "foo1"), ImmutableSet.of("baz"));
+    assertThat(base.withAdditionalFixedVariables(ImmutableMap.of())).isSameInstanceAs(base);
+    assertThat(base.withAdditionalVariables(ImmutableMap.of(), ImmutableSet.of()))
+        .isSameInstanceAs(base);
+  }
 }