diff --git a/lib/minify.js b/lib/minify.js
index fdc48961..73f0e456 100644
--- a/lib/minify.js
+++ b/lib/minify.js
@@ -77,7 +77,7 @@ function minify(files, options) {
         set_shorthand("ie8", options, [ "compress", "mangle", "output" ]);
         set_shorthand("keep_classnames", options, [ "compress", "mangle" ]);
         set_shorthand("keep_fnames", options, [ "compress", "mangle" ]);
-        set_shorthand("module", options, [ "compress" ]);
+        set_shorthand("module", options, [ "compress", "mangle" ]);
         set_shorthand("safari10", options, [ "mangle", "output" ]);
         set_shorthand("toplevel", options, [ "compress", "mangle" ]);
         set_shorthand("warnings", options, [ "compress" ]);
diff --git a/lib/scope.js b/lib/scope.js
index 09687aaf..de572f3e 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -110,7 +110,11 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
 
     // pass 1: setup scope chaining and handle definitions
     var self = this;
-    var scope = self.parent_scope = null;
+    var scope = null;
+    if (options.module) {
+        scope = new AST_Scope(self);
+    }
+    self.parent_scope = scope;
     var labels = new Dictionary();
     var defun = null;
     var in_destructuring = null;
diff --git a/test/compress/harmony.js b/test/compress/harmony.js
index 7d2fdb93..c0eaab44 100644
--- a/test/compress/harmony.js
+++ b/test/compress/harmony.js
@@ -1617,3 +1617,15 @@ module_enables_strict_mode: {
         }
     }
 }
+
+module_mangle_scope: {
+    mangle = {
+        module: true
+    }
+    input: {
+        let a = 10;
+    }
+    expect: {
+        let e = 10;
+    }
+}