diff --git a/lib/ace/keyboard/emacs.js b/lib/ace/keyboard/emacs.js
index 7e855959..f1adb9ef 100644
--- a/lib/ace/keyboard/emacs.js
+++ b/lib/ace/keyboard/emacs.js
@@ -219,6 +219,10 @@ exports.handler.bindKey = function(key, command) {
 };
 
 exports.handler.handleKeyboard = function(data, hashId, key, keyCode) {
+    // if keyCode == -1 a non-printable key was pressed, such as just
+    // control. Handling those is currently not supported in this handler
+    if (keyCode === -1) return undefined;
+
     var editor = data.editor;
     // insertstring data.count times
     if (hashId == -1) {