diff --git a/src/thread/pthread/SDL_sysmutex.c b/src/thread/pthread/SDL_sysmutex.c
index 07a5ddc81..d7fa982c8 100644
--- a/src/thread/pthread/SDL_sysmutex.c
+++ b/src/thread/pthread/SDL_sysmutex.c
@@ -23,8 +23,8 @@
 #ifndef _GNU_SOURCE
 #define _GNU_SOURCE
 #endif
-#include <pthread.h>
 #include <errno.h>
+#include <pthread.h>
 
 #include "SDL_thread.h"
 
diff --git a/src/thread/pthread/SDL_syssem.c b/src/thread/pthread/SDL_syssem.c
index 7e0ad0423..a89a262a7 100644
--- a/src/thread/pthread/SDL_syssem.c
+++ b/src/thread/pthread/SDL_syssem.c
@@ -20,6 +20,9 @@
 */
 #include "../../SDL_internal.h"
 
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
 #include <errno.h>
 #include <pthread.h>
 #include <semaphore.h>