diff --git a/lib/ace/keyboard/emacs.js b/lib/ace/keyboard/emacs.js
index 7e47eb2c..65fc5840 100644
--- a/lib/ace/keyboard/emacs.js
+++ b/lib/ace/keyboard/emacs.js
@@ -178,8 +178,7 @@ exports.handler.handleKeyboard = function(data, hashId, key, keyCode) {
         }
     }
 
-    if (key == "\x00")
-        return;
+    if (key == "\x00") return undefined;
 
     var modifier = eMods[hashId];
 
@@ -207,7 +206,7 @@ exports.handler.handleKeyboard = function(data, hashId, key, keyCode) {
     data.keyChain = command == "null" ? key : "";
 
     // there really is no command
-    if (!command) return;
+    if (!command) return undefined;
 
     // we pass b/c of key combo or universalArgument
     if (command === "null") return {command: "null"};
@@ -237,6 +236,7 @@ exports.handler.handleKeyboard = function(data, hashId, key, keyCode) {
             editor.setEmacsMarkMode(null);
         }
         command = this.commands[command] || editor.commands.commands[command];
+        if (!command) return undefined;
     }
 
     if (!command.readonly && !command.isYank)