diff --git a/include/ui/Rect.h b/include/ui/Rect.h
index bd82061..308da7b 100644
--- a/include/ui/Rect.h
+++ b/include/ui/Rect.h
@@ -147,7 +147,7 @@
     // a ROT90 then the output rectangle is defined in a space extending to
     // (height, width).  Otherwise the output rectangle is in the same space as
     // the input.
-    Rect transform(uint32_t xform, int32_t width, int32_t height);
+    Rect transform(uint32_t xform, int32_t width, int32_t height) const;
 };
 
 ANDROID_BASIC_TYPES_TRAITS(Rect)