diff --git a/demo/foo.c b/demo/foo.c
index d0661166..4b677399 100644
--- a/demo/foo.c
+++ b/demo/foo.c
@@ -20,7 +20,7 @@ USA. */
 
 #define _LIBFOO_COMPILATION_
 #include "foo.h"
-#undef _LIBFOO_COMPILATION
+#undef _LIBFOO_COMPILATION_
 
 #include <stdio.h>