diff --git a/tests/Regression/bz529997-sem_timedwait-with-invalid-time/real-reproducer.c b/tests/Regression/bz529997-sem_timedwait-with-invalid-time/real-reproducer.c
index 471fe16..c01a116 100644
--- a/tests/Regression/bz529997-sem_timedwait-with-invalid-time/real-reproducer.c
+++ b/tests/Regression/bz529997-sem_timedwait-with-invalid-time/real-reproducer.c
@@ -5,6 +5,7 @@
 #include <time.h>
 #include <errno.h>
 #include <string.h>
+#include <unistd.h>
 
 void func(sem_t *semp)
 {