diff --git a/src/plugins/imapsieve/imap-sieve-storage.c b/src/plugins/imapsieve/imap-sieve-storage.c
index 00d97ae93a40161dfe25796d041561029c3eb76b..5bd57bc46ade1d51e3278b087f758eed1f1ba8a1 100644
--- a/src/plugins/imapsieve/imap-sieve-storage.c
+++ b/src/plugins/imapsieve/imap-sieve-storage.c
@@ -1013,7 +1013,7 @@ imap_sieve_mailbox_rule_match_cause
 {
 	const char *const *cp;
 
-	if (rule->causes == NULL || *rule->causes == '\0')
+	if (rule->causes == NULL || *rule->causes == NULL)
 		return TRUE;
 
 	for (cp = rule->causes; *cp != NULL; cp++) {