diff --git a/src/http_rules.c b/src/http_rules.c
index 3186036..6ad1e9c 100644
--- a/src/http_rules.c
+++ b/src/http_rules.c
@@ -408,6 +408,10 @@
 	}
 
 	rule = calloc(1, sizeof(*rule));
+	if (!rule) {
+		memprintf(errmsg, "parsing [%s:%d]: out of memory.", file, linenum);
+		return NULL;
+	}
 	rule->cond = cond;
 	LIST_INIT(&rule->rdr_fmt);