diff --git a/include/common/h1.h b/include/common/h1.h
index b36f6fa..0d652e7 100644
--- a/include/common/h1.h
+++ b/include/common/h1.h
@@ -202,6 +202,9 @@
 	const char *ptr = b_peek(buf, start);
 	int bytes = 1;
 
+	if (stop <= start)
+		return 0;
+
 	/* NB: we'll check data availability at the end. It's not a
 	 * problem because whatever we match first will be checked
 	 * against the correct length.