diff --git a/include/internal/conf.h b/include/internal/conf.h
index 71b75ddc07..3f1c30f3e1 100644
--- a/include/internal/conf.h
+++ b/include/internal/conf.h
@@ -38,7 +38,7 @@
  */
 
 #ifndef HEADER_INTERNAL_CONF_H
-# define INTERNAL_CONF_H
+# define HEADER_INTERNAL_CONF_H
 
 #include <openssl/conf.h>