diff --git a/mode/gfm/gfm.js b/mode/gfm/gfm.js
index 80a8e2c84da5ef933af0d8594cc83a418315b4c2..94ff920bfb7d9fb643b525de5352bd20952d92f8 100644
--- a/mode/gfm/gfm.js
+++ b/mode/gfm/gfm.js
@@ -116,8 +116,9 @@ CodeMirror.defineMode("gfm", function(config, modeConfig) {
     markdownConfig[attr] = modeConfig[attr];
   }
   markdownConfig.name = "markdown";
-  CodeMirror.defineMIME("gfmBase", markdownConfig);
-  return CodeMirror.overlayMode(CodeMirror.getMode(config, "gfmBase"), gfmOverlay);
+  return CodeMirror.overlayMode(CodeMirror.getMode(config, markdownConfig), gfmOverlay);
+
 }, "markdown");
 
+  CodeMirror.defineMIME("text/x-gfm", "gfm");
 });