diff --git a/mozilla/layout/forms/nsListControlFrame.cpp b/mozilla/layout/forms/nsListControlFrame.cpp
index bd7a950e7b5..62e5fbd279f 100644
--- a/mozilla/layout/forms/nsListControlFrame.cpp
+++ b/mozilla/layout/forms/nsListControlFrame.cpp
@@ -311,6 +311,7 @@ nsListControlFrame::nsListControlFrame(nsIPresShell* aShell,
 
   mDummyFrame                  = nsnull;
 
+  mControlSelectMode           = PR_FALSE;
   REFLOW_COUNTER_INIT()
 }
 
@@ -3025,7 +3026,15 @@ nsListControlFrame::KeyPress(nsIDOMEvent* aKeyEvent)
   // DOM_VK_ESCAPE cancels the selection
   // default processing checks to see if the pressed the first 
   //   letter of an item in the list and advances to it
-
+  
+  if (isControl && (keycode == nsIDOMKeyEvent::DOM_VK_UP ||
+                    keycode == nsIDOMKeyEvent::DOM_VK_LEFT ||
+                    keycode == nsIDOMKeyEvent::DOM_VK_DOWN ||
+                    keycode == nsIDOMKeyEvent::DOM_VK_RIGHT)) {
+    mControlSelectMode = PR_TRUE;
+  } else if (charcode != ' ') {
+    mControlSelectMode = PR_FALSE;
+  }
   switch (keycode) {
 
     case nsIDOMKeyEvent::DOM_VK_UP:
@@ -3205,6 +3214,8 @@ nsListControlFrame::KeyPress(nsIDOMEvent* aKeyEvent)
       mStartSelectionIndex = newIndex;
       mEndSelectionIndex = newIndex;
       ScrollToIndex(newIndex);
+    } else if (mControlSelectMode && charcode == ' ') {
+      SingleSelection(newIndex, PR_TRUE);
     } else {
       PRBool wasChanged = PerformSelection(newIndex, isShift, isControl);
       if (wasChanged) {
diff --git a/mozilla/layout/forms/nsListControlFrame.h b/mozilla/layout/forms/nsListControlFrame.h
index 48a3fb374b3..234a96f77b9 100644
--- a/mozilla/layout/forms/nsListControlFrame.h
+++ b/mozilla/layout/forms/nsListControlFrame.h
@@ -265,13 +265,13 @@ protected:
   PRInt32      mEndSelectionIndex;
 
   nsIComboboxControlFrame *mComboboxFrame;
-  PRPackedBool mChangesSinceDragStart;
-  PRPackedBool mButtonDown;
   nscoord      mMaxWidth;
   nscoord      mMaxHeight;
   PRInt32      mNumDisplayRows;
+  PRPackedBool mChangesSinceDragStart;
+  PRPackedBool mButtonDown;
 
-  PRBool       mIsAllContentHere;
+  PRPackedBool mIsAllContentHere;
   PRPackedBool mIsAllFramesHere;
   PRPackedBool mHasBeenInitialized;
   PRPackedBool mNeedToReset;
@@ -279,6 +279,9 @@ protected:
 
   PRPackedBool mOverrideReflowOpt;
 
+  //bool value for multiple discontiguous selection
+  PRPackedBool mControlSelectMode;
+
   nsRefPtr<nsListEventListener> mEventListener;
 
   PRInt16 mPassId;