diff --git a/include/SDL_config.h.cmake b/include/SDL_config.h.cmake
index 043817f44..3c8edffec 100644
--- a/include/SDL_config.h.cmake
+++ b/include/SDL_config.h.cmake
@@ -64,6 +64,7 @@
 #cmakedefine HAVE_MEMORY_H 1
 #cmakedefine HAVE_SIGNAL_H 1
 #cmakedefine HAVE_STDARG_H 1
+#cmakedefine HAVE_STDDEF_H 1
 #cmakedefine HAVE_STDINT_H 1
 #cmakedefine HAVE_STDIO_H 1
 #cmakedefine HAVE_STDLIB_H 1