diff --git a/dlls/winemac.drv/cocoa_window.m b/dlls/winemac.drv/cocoa_window.m
index 61a6ab2cd4e..1a73deedc2c 100644
--- a/dlls/winemac.drv/cocoa_window.m
+++ b/dlls/winemac.drv/cocoa_window.m
@@ -2338,7 +2338,7 @@ - (void) grabDockIconSnapshotFromWindow:(WineWindow*)window force:(BOOL)force
                 return;
         }
 
-        const void* windowID = (const void*)(CGWindowID)window.windowNumber;
+        const void* windowID = (const void*)(uintptr_t)(CGWindowID)window.windowNumber;
         CFArrayRef windowIDs = CFArrayCreate(NULL, &windowID, 1, NULL);
         CGImageRef windowImage = CGWindowListCreateImageFromArray(CGRectNull, windowIDs, kCGWindowImageBoundsIgnoreFraming);
         CFRelease(windowIDs);