diff --git a/javascript/extractor/src/com/semmle/js/extractor/ASTExtractor.java b/javascript/extractor/src/com/semmle/js/extractor/ASTExtractor.java
index 573b65c40d0..886cacd87a6 100644
--- a/javascript/extractor/src/com/semmle/js/extractor/ASTExtractor.java
+++ b/javascript/extractor/src/com/semmle/js/extractor/ASTExtractor.java
@@ -553,7 +553,7 @@ public class ASTExtractor {
 			if (sourceType.hasLocalScope()) {
 				Label moduleScopeKey = trapwriter.globalID("module;{" + locationManager.getFileLabel() + "}," + locationManager.getStartLine() + "," + locationManager.getStartColumn());
 				scopeManager.enterScope(3, moduleScopeKey, toplevelLabel);
-				scopeManager.addVariables(sourceType.getPredefinedLocals(platform));
+				scopeManager.addVariables(sourceType.getPredefinedLocals(platform, locationManager.getSourceFileExtension()));
 				trapwriter.addTuple("isModule", toplevelLabel);
 			}
 
diff --git a/javascript/extractor/src/com/semmle/js/extractor/ExtractorConfig.java b/javascript/extractor/src/com/semmle/js/extractor/ExtractorConfig.java
index f5de7e8bb05..bd42953e240 100644
--- a/javascript/extractor/src/com/semmle/js/extractor/ExtractorConfig.java
+++ b/javascript/extractor/src/com/semmle/js/extractor/ExtractorConfig.java
@@ -107,14 +107,14 @@ public class ExtractorConfig {
          * <p/>
          * If this source type has no local scope, the empty set is returned.
          */
-        public Set<String> getPredefinedLocals(Platform platform) {
+        public Set<String> getPredefinedLocals(Platform platform, String extension) {
             switch (this) {
             case CLOSURE_MODULE:
                 return closureLocals;
             case COMMONJS_MODULE:
                 return commonJsLocals;
             case MODULE:
-                if (platform == Platform.NODE) {
+                if (platform == Platform.NODE && !extension.equals(".mjs")) {
                     // An ES2015 module that is compiled to a Node.js module effectively has the locals
                     // from Node.js even if they are not part of the ES2015 standard.
                     return commonJsLocals;