diff --git a/guacamole-common-js/src/main/webapp/modules/Keyboard.js b/guacamole-common-js/src/main/webapp/modules/Keyboard.js
index 49edcf5e1..f71ca8af3 100644
--- a/guacamole-common-js/src/main/webapp/modules/Keyboard.js
+++ b/guacamole-common-js/src/main/webapp/modules/Keyboard.js
@@ -97,6 +97,15 @@ Guacamole.Keyboard = function(element) {
          */
         this.keysym = null;
 
+        /**
+         * Whether the keysym value of this key event is known to be reliable.
+         * If false, the keysym may still be valid, but it's only a best guess,
+         * and future key events may be a better source of information.
+         *
+         * @type Boolean
+         */
+        this.reliable = false;
+
         /**
          * Returns the number of milliseconds elapsed since this event was
          * received.
@@ -169,6 +178,10 @@ Guacamole.Keyboard = function(element) {
         this.keysym =  keysym_from_key_identifier(key, location)
                     || keysym_from_keycode(keyCode, location);
 
+        // DOM3 and keyCode are reliable sources
+        if (this.keysym)
+            this.reliable = true;
+
         // We must use the (potentially buggy) keyIdentifier immediately if
         // keypress will likely not fire, as we need to make a best effort
         // to prevent default if requested
@@ -212,6 +225,9 @@ Guacamole.Keyboard = function(element) {
         // Pull keysym from char code
         this.keysym = keysym_from_charcode(charCode);
 
+        // Keypress is always reliable
+        this.reliable = true;
+
     };
 
     KeypressEvent.prototype = new KeyEvent();
@@ -276,6 +292,9 @@ Guacamole.Keyboard = function(element) {
                     || keysym_from_keycode(keyCode, location)
                     || recentKeysym[keyCode];
 
+        // Keyup is as reliable as it will ever be
+        this.reliable = true;
+
     };
 
     KeyupEvent.prototype = new KeyEvent();