diff --git a/assert/test-assert-2.c b/assert/test-assert-2.c
index 99f8f683e8..3288609ab2 100644
--- a/assert/test-assert-2.c
+++ b/assert/test-assert-2.c
@@ -27,6 +27,7 @@
 #include <dlfcn.h>
 #include <string.h>
 #include <signal.h>
+#include <unistd.h>
 
 #undef NDEBUG
 #include <assert.h>