diff --git a/hw/xquartz/X11Application.m b/hw/xquartz/X11Application.m
index ed9fb32b1..805ed9933 100644
--- a/hw/xquartz/X11Application.m
+++ b/hw/xquartz/X11Application.m
@@ -1030,23 +1030,32 @@ static inline int ensure_flag(int flags, int device_independent, int device_depe
     if(isMouseOrTabletEvent) {
         static NSPoint lastpt;
         NSWindow *window = [e window];
-        NSRect screen = [[[NSScreen screens] objectAtIndex:0] frame];;
+        NSRect screen = [[[NSScreen screens] objectAtIndex:0] frame];
+	    BOOL hasUntrustedPointerDelta;
+        
+        // NSEvents for tablets are not consistent wrt deltaXY between events, so we cannot rely on that
+        // Thus tablets will be subject to the warp-pointer bug worked around by the delta, but tablets
+        // are not normally used in cases where that bug would present itself, so this is a fair tradeoff
+        // <rdar://problem/7111003> deltaX and deltaY are incorrect for NSMouseMoved, NSTabletPointEventSubtype
+        // http://xquartz.macosforge.org/trac/ticket/288
+        hasUntrustedPointerDelta = isTabletEvent;
+        
+        // The deltaXY for middle click events also appear erroneous after fast user switching
+        // <rdar://problem/7979468> deltaX and deltaY are incorrect for NSOtherMouseDown and NSOtherMouseUp after FUS
+        // http://xquartz.macosforge.org/trac/ticket/389
+        hasUntrustedPointerDelta = hasUntrustedPointerDelta || [e type] == NSOtherMouseDown || [e type] == NSOtherMouseUp;
 
+        // The deltaXY for scroll events correspond to the scroll delta, not the pointer delta
+        // <rdar://problem/7989690> deltaXY for wheel events are being sent as mouse movement
+        hasUntrustedPointerDelta = hasUntrustedPointerDelta || [e type] == NSScrollWheel;
+        
         if (window != nil)	{
             NSRect frame = [window frame];
             location = [e locationInWindow];
             location.x += frame.origin.x;
             location.y += frame.origin.y;
             lastpt = location;
-        } else if(isTabletEvent || [e type] == NSOtherMouseDown || [e type] == NSOtherMouseUp) {
-            // NSEvents for tablets are not consistent wrt deltaXY between events, so we cannot rely on that
-            // Thus tablets will be subject to the warp-pointer bug worked around by the delta, but tablets
-            // are not normally used in cases where that bug would present itself, so this is a fair tradeoff
-            // <rdar://problem/7111003> deltaX and deltaY are incorrect for NSMouseMoved, NSTabletPointEventSubtype
-            // http://xquartz.macosforge.org/trac/ticket/288
-            // The deltaXY for middle click events also appear erroneous after fast user switching
-            // <rdar://problem/7979468> deltaX and deltaY are incorrect for NSOtherMouseDown and NSOtherMouseUp after FUS
-            // http://xquartz.macosforge.org/trac/ticket/389
+        } else if(hasUntrustedPointerDelta) {
             location = [e locationInWindow];
             lastpt = location;
         } else {