diff --git a/lib/h264.cpp b/lib/h264.cpp
index 20d961b8..1efa2cec 100644
--- a/lib/h264.cpp
+++ b/lib/h264.cpp
@@ -1,4 +1,6 @@
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 #include "h264.h"
 #include <cstdlib>
 #include <cstring>
diff --git a/lib/nal.cpp b/lib/nal.cpp
index a28edd23..25ae8d7f 100644
--- a/lib/nal.cpp
+++ b/lib/nal.cpp
@@ -1,4 +1,6 @@
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 #include <cstdlib>
 #include <cstring>
 #include <math.h>//for log