diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Environment.java b/src/main/java/com/google/devtools/build/lib/syntax/Environment.java
index fcd0b23..1978ba5 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Environment.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Environment.java
@@ -612,7 +612,10 @@
   }
 
   /**
-   * A Builder class for Environment
+   * A Builder class for Environment.
+   *
+   * <p>The caller must explicitly set the semantics by calling either {@link #setSemantics} or
+   * {@link #useDefaultSemantics}.
    */
   public static class Builder {
     private final Mutability mutability;
@@ -655,6 +658,11 @@
       return this;
     }
 
+    public Builder useDefaultSemantics() {
+      this.semantics = SkylarkSemantics.DEFAULT_SEMANTICS;
+      return this;
+    }
+
     /** Sets an EventHandler for errors and warnings. */
     public Builder setEventHandler(EventHandler eventHandler) {
       Preconditions.checkState(this.eventHandler == null);