diff --git a/tests/unistd/fork.c b/tests/unistd/fork.c
index eb9b84ac2d..225ead36e2 100644
--- a/tests/unistd/fork.c
+++ b/tests/unistd/fork.c
@@ -1,3 +1,4 @@
+#include <pthread.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>