diff --git a/nfq/protocol.c b/nfq/protocol.c
index 4013ba9..cedf15d 100644
--- a/nfq/protocol.c
+++ b/nfq/protocol.c
@@ -525,9 +525,9 @@ bool QUICExtractHostFromInitial(const uint8_t *data, size_t data_len, char *host
 bool IsQUICInitial(const uint8_t *data, size_t len)
 {
 	// too small packets are not likely to be initials with client hello
-	if (len < 256) return false;
+	// long header, fixed bit
+	if (len < 256 || (data[0] & 0xC0)!=0xC0) return false;
 
-	// this also ensures long header
 	uint32_t ver = QUICExtractVersion(data,len);
 	if (QUICDraftVersion(ver) < 11) return false;