diff --git a/quic/core/quic_framer.cc b/quic/core/quic_framer.cc
index 31af81a..fba4287 100644
--- a/quic/core/quic_framer.cc
+++ b/quic/core/quic_framer.cc
@@ -423,6 +423,9 @@
       current_received_frame_type_(0) {
   DCHECK(!supported_versions.empty());
   version_ = supported_versions_[0];
+  DCHECK(version_.transport_version != QUIC_VERSION_UNSUPPORTED ||
+         !GetQuicRestartFlag(quic_fix_handling_of_bad_prox_packet))
+      << ParsedQuicVersionVectorToString(supported_versions_);
 }
 
 QuicFramer::~QuicFramer() {}