diff --git a/src/thread/linux/SDL_syssem.c b/src/thread/linux/SDL_syssem.c
index b62038d67..b272abf00 100644
--- a/src/thread/linux/SDL_syssem.c
+++ b/src/thread/linux/SDL_syssem.c
@@ -54,6 +54,7 @@ static char rcsid =
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>			/* For getpid() */
+#include <pthread.h>
 #include <semaphore.h>
 
 /* Wrapper around POSIX 1003.1b semaphores */