diff --git a/src/shared/tests.h b/src/shared/tests.h
index 07e05bf2676ae..1572ca71022f0 100644
--- a/src/shared/tests.h
+++ b/src/shared/tests.h
@@ -3,6 +3,7 @@
 
 #include <stdbool.h>
 #include <sys/prctl.h>
+#include <unistd.h>
 
 #include "sd-daemon.h"