diff --git a/docs/changes.txt b/docs/changes.txt
index c5d0b669d0..3827c1c331 100644
--- a/docs/changes.txt
+++ b/docs/changes.txt
@@ -26,6 +26,12 @@ Changes in behaviour not resulting in compilation errors, please read this!
 Changes in behaviour which may result in compilation errors
 -----------------------------------------------------------
 
+- Some classes (notably wxBitmap and wxImage) don't define operator==() as it
+  used to work in somewhat unexpected way as it compared only internal pointers
+  and not the object data. The code using it will have to be updated:
+  * If the object was compared with wxNullXXX, use IsOk() method instead
+  * If valid object need to be compated, use IsRefTo() to reproduce the old
+    behaviour or change the code to avoid comparing bitmaps &c
 - wxFontData::GetColour() now returns a const colour.
 - wxDC objects can't be created directly now (this never worked, now it doesn't
   even compile).