diff --git a/GLFW-4.0-sketchbook.md b/GLFW-4.0-sketchbook.md
index 2294844..16617ee 100644
--- a/GLFW-4.0-sketchbook.md
+++ b/GLFW-4.0-sketchbook.md
@@ -21,4 +21,5 @@
 - Unify `GLFW*proc` to `GLFWproc`
 - Add `APIENTRY` to `GLFWproc`
 - Sane function pointer typedefs
-- Move to enums for tokens
\ No newline at end of file
+- Move to enums for tokens
+- Add return value error indication where possible
\ No newline at end of file