diff --git a/main.c b/main.c
index 3d9bb3b..c49deae 100644
--- a/main.c
+++ b/main.c
@@ -9,7 +9,7 @@
 #include "msd/start.h"
 
 /* Assume BSD without native fmemopen() if doesn't seem to be glibc */
-#if defined(__APPLE__) || !defined(_GNU_SOURCE) || !defined(_POSIX_C_SOURCE) || _POSIX_C_SOURCE < 200809L
+#if defined(__APPLE__) || (!defined(_GNU_SOURCE) && (!defined(_POSIX_C_SOURCE) || _POSIX_C_SOURCE < 200809L))
 #include "fmemopen.c" // BSD fmemopen() compat in terms of funopen()
 #endif