diff --git a/gfx/thebes/gfxRect.h b/gfx/thebes/gfxRect.h
index 0720500a6d8e..d40104671b64 100644
--- a/gfx/thebes/gfxRect.h
+++ b/gfx/thebes/gfxRect.h
@@ -137,8 +137,8 @@ struct THEBES_API gfxRect {
         Inset(sides[0], sides[1], sides[2], sides[3]);
     }
 
-    void Inset(const gfxIntSize& size) {
-        Inset(size.height, size.width, size.height, size.width);
+    void Inset(const gfxIntSize& aSize) {
+        Inset(aSize.height, aSize.width, aSize.height, aSize.width);
     }
 
     void Outset(gfxFloat k) {
@@ -159,8 +159,8 @@ struct THEBES_API gfxRect {
         Outset(sides[0], sides[1], sides[2], sides[3]);
     }
 
-    void Outset(const gfxIntSize& size) {
-        Outset(size.height, size.width, size.height, size.width);
+    void Outset(const gfxIntSize& aSize) {
+        Outset(aSize.height, aSize.width, aSize.height, aSize.width);
     }
 
     // Round the rectangle edges to integer coordinates, such that the rounded