gopherjs
diff --git a/‎compiler/gopherjspkg/fs_vfsdata.go
Lines changed: 1 addition & 1 deletion b/‎compiler/gopherjspkg/fs_vfsdata.go
Lines changed: 1 addition & 1 deletion
diff --git a/‎compiler/prelude/jsmapping.go
Lines changed: 3 additions & 0 deletions b/‎compiler/prelude/jsmapping.go
Lines changed: 3 additions & 0 deletions
diff --git a/‎compiler/prelude/prelude_min.go
Lines changed: 1 addition & 1 deletion b/‎compiler/prelude/prelude_min.go
Lines changed: 1 addition & 1 deletion
diff --git a/‎tests/js_test.go
Lines changed: 5 additions & 5 deletions b/‎tests/js_test.go
Lines changed: 5 additions & 5 deletions
@@ -60,6 +60,9 @@ var $externalize = function(v, t, makeWrapper) {
     }
     return $externalize(v.$val, v.constructor, makeWrapper);
   case $kindMap:
+    if (v.keys === undefined) {
+      return null;
+    }
     var m = {};
     var keys = Array.from(v.keys());
     for (var i = 0; i < keys.length; i++) {
 
@@ -688,11 +688,11 @@ func TestExternalize(t *testing.T) {
 			input: true,
 			want:  "true",
 		},
-		// {
-		// 	name:  "nil map",
-		// 	input: func() map[string]string { return nil }(),
-		// 	want:  "null",
-		// },
+		{
+			name:  "nil map",
+			input: func() map[string]string { return nil }(),
+			want:  "null",
+		},
 		{
 			name:  "empty map",
 			input: map[string]string{},