diff --git a/tests/libtest/lib518.c b/tests/libtest/lib518.c
index bb09f0ffc..62016a279 100644
--- a/tests/libtest/lib518.c
+++ b/tests/libtest/lib518.c
@@ -29,7 +29,7 @@
 #ifdef HAVE_FCNTL_H
 #include <fcntl.h>
 #endif
-#ifdef UNISTD_H
+#ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif