--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -4874,16 +4874,21 @@ GetIntegerDeltaForEvent(NSEvent* aEvent)
                     forEvent:theEvent];
   } else if (phase & (NSEventPhaseEnded | NSEventPhaseCancelled)) {
     [self sendWheelCondition:NO
                        first:eWheelOperationStart
                       second:eWheelOperationEnd
                     forEvent:theEvent];
   }
 
+  if (!mGeckoChild) {
+    return;
+  }
+  RefPtr<nsChildView> geckoChildDeathGrip(mGeckoChild);
+
   NSPoint locationInWindow = nsCocoaUtils::EventLocationForWindow(theEvent, [self window]);
 
   ScreenPoint position = ViewAs<ScreenPixel>(
     [self convertWindowCoordinates:locationInWindow],
     PixelCastJustification::LayoutDeviceIsScreenForUntransformedEvent);
 
   bool usePreciseDeltas = nsCocoaUtils::HasPreciseScrollingDeltas(theEvent) &&
     Preferences::GetBool("mousewheel.enable_pixel_scrolling", true);
@@ -4896,17 +4901,17 @@ GetIntegerDeltaForEvent(NSEvent* aEvent)
   NSTimeInterval beforeNow = [[NSProcessInfo processInfo] systemUptime] - [theEvent timestamp];
   PRIntervalTime eventIntervalTime = PR_IntervalNow() - PR_MillisecondsToInterval(beforeNow * 1000);
   TimeStamp eventTimeStamp = TimeStamp::Now() - TimeDuration::FromSeconds(beforeNow);
 
   ScreenPoint preciseDelta;
   if (usePreciseDeltas) {
     CGFloat pixelDeltaX = 0, pixelDeltaY = 0;
     nsCocoaUtils::GetScrollingDeltas(theEvent, &pixelDeltaX, &pixelDeltaY);
-    double scale = mGeckoChild->BackingScaleFactor();
+    double scale = geckoChildDeathGrip->BackingScaleFactor();
     preciseDelta = ScreenPoint(-pixelDeltaX * scale, -pixelDeltaY * scale);
   }
 
   if (usePreciseDeltas && hasPhaseInformation) {
     PanGestureInput panEvent(PanGestureTypeForEvent(theEvent),
                              eventIntervalTime, eventTimeStamp,
                              position, preciseDelta, modifiers);
     panEvent.mLineOrPageDeltaX = lineOrPageDelta.x;
@@ -4923,45 +4928,45 @@ GetIntegerDeltaForEvent(NSEvent* aEvent)
       if (nextWheelEvent &&
           PanGestureTypeForEvent(nextWheelEvent) == PanGestureInput::PANGESTURE_MOMENTUMSTART) {
         panEvent.mFollowedByMomentum = true;
       }
     }
 
     bool canTriggerSwipe = [self shouldConsiderStartingSwipeFromEvent:theEvent];
     panEvent.mRequiresContentResponseIfCannotScrollHorizontallyInStartDirection = canTriggerSwipe;
-    mGeckoChild->DispatchAPZWheelInputEvent(panEvent, canTriggerSwipe);
+    geckoChildDeathGrip->DispatchAPZWheelInputEvent(panEvent, canTriggerSwipe);
   } else if (usePreciseDeltas) {
     // This is on 10.6 or old touchpads that don't have any phase information.
     ScrollWheelInput wheelEvent(eventIntervalTime, eventTimeStamp, modifiers,
                                 ScrollWheelInput::SCROLLMODE_INSTANT,
                                 ScrollWheelInput::SCROLLDELTA_PIXEL,
                                 position,
                                 preciseDelta.x,
                                 preciseDelta.y,
                                 false);
     wheelEvent.mLineOrPageDeltaX = lineOrPageDelta.x;
     wheelEvent.mLineOrPageDeltaY = lineOrPageDelta.y;
     wheelEvent.mIsMomentum = nsCocoaUtils::IsMomentumScrollEvent(theEvent);
-    mGeckoChild->DispatchAPZWheelInputEvent(wheelEvent, false);
+    geckoChildDeathGrip->DispatchAPZWheelInputEvent(wheelEvent, false);
   } else {
     ScrollWheelInput::ScrollMode scrollMode = ScrollWheelInput::SCROLLMODE_INSTANT;
     if (gfxPrefs::SmoothScrollEnabled() && gfxPrefs::WheelSmoothScrollEnabled()) {
       scrollMode = ScrollWheelInput::SCROLLMODE_SMOOTH;
     }
     ScrollWheelInput wheelEvent(eventIntervalTime, eventTimeStamp, modifiers,
                                 scrollMode,
                                 ScrollWheelInput::SCROLLDELTA_LINE,
                                 position,
                                 lineOrPageDelta.x,
                                 lineOrPageDelta.y,
                                 false);
     wheelEvent.mLineOrPageDeltaX = lineOrPageDelta.x;
     wheelEvent.mLineOrPageDeltaY = lineOrPageDelta.y;
-    mGeckoChild->DispatchAPZWheelInputEvent(wheelEvent, false);
+    geckoChildDeathGrip->DispatchAPZWheelInputEvent(wheelEvent, false);
   }
 
   NS_OBJC_END_TRY_ABORT_BLOCK;
 }
 
 - (void)handleAsyncScrollEvent:(CGEventRef)cgEvent ofType:(CGEventType)type
 {
   IAPZCTreeManager* apzctm = [self apzctm];