diff --git a/desmume/src/libretro-common/rthreads/rthreads.c b/desmume/src/libretro-common/rthreads/rthreads.c
index e2238823b..85cb776ae 100644
--- a/desmume/src/libretro-common/rthreads/rthreads.c
+++ b/desmume/src/libretro-common/rthreads/rthreads.c
@@ -22,6 +22,7 @@
 
 #ifdef __unix__
 #define _POSIX_C_SOURCE 199309
+#define _GNU_SOURCE
 #endif
 
 #include <stdlib.h>