diff --git a/AppKit/CPStringDrawing.j b/AppKit/CPStringDrawing.j
index fbd174592..68eea2803 100644
--- a/AppKit/CPStringDrawing.j
+++ b/AppKit/CPStringDrawing.j
@@ -60,7 +60,7 @@ var CPStringSizeWithFontInWidthCache = {};
         CPStringSizeWithFontInWidthCache[cacheKey] = size;
     }
 
-    return size;
+    return CGSizeMakeCopy(size);
 }