diff --git a/src/tcpcheck.c b/src/tcpcheck.c
index 55fd190cf..117be3275 100644
--- a/src/tcpcheck.c
+++ b/src/tcpcheck.c
@@ -2047,6 +2047,13 @@ enum tcpcheck_eval_ret tcpcheck_eval_expect(struct check *check, struct tcpcheck
 		break;
 
 	case TCPCHK_EXPECT_CUSTOM:
+		/* Don't eval custom function if the buffer is empty. It means
+		 * cusstom functions can't expect an empty response. If this
+		 * change, don't forget to change this test and update all
+		 * custom functions.
+		 */
+		if (!b_data(&check->bi))
+			break;
 		if (expect->custom)
 			ret = expect->custom(check, rule, last_read);
 		goto out;