diff --git a/include/postwin.h b/include/postwin.h
index 8a17ae5106cf..95cd6f836ca3 100644
--- a/include/postwin.h
+++ b/include/postwin.h
@@ -23,6 +23,7 @@
 #undef CompareString
 #undef CopyFile
 #undef DELETE
+#undef DocumentProperties
 #undef DrawText
 #undef FindWindow
 #undef Folder