diff --git a/bin/tests/sym_test.c b/bin/tests/sym_test.c
index 9f245d7e51..d8912feb34 100644
--- a/bin/tests/sym_test.c
+++ b/bin/tests/sym_test.c
@@ -20,6 +20,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 #include <isc/assertions.h>
 #include <isc/result.h>