diff --git a/tests/sms/sms_test.c b/tests/sms/sms_test.c
index 9ca83a5..912c082 100644
--- a/tests/sms/sms_test.c
+++ b/tests/sms/sms_test.c
@@ -215,7 +215,7 @@
 	},
 };
 
-static void test_octet_return()
+static void test_octet_return(void)
 {
 	char out[256];
 	int oct, septets;