diff --git a/Lib/fontTools/colorLib/builder.py b/Lib/fontTools/colorLib/builder.py
index 4d8e5fa63..9d62d497f 100644
--- a/Lib/fontTools/colorLib/builder.py
+++ b/Lib/fontTools/colorLib/builder.py
@@ -539,7 +539,7 @@ class LayerCollector:
             except KeyError:
                 raise NotImplementedError(fmt)
         raise TypeError(
-            f"expected int, Mapping or ot.Paint, found {type(paint).__name__}: {paint!r}"
+            f"Not sure what to do with {type(paint).__name__}: {paint!r}"
         )