diff --git a/src/net/spdy/spdy_proxy_client_socket.cc b/src/net/spdy/spdy_proxy_client_socket.cc
index 33d35bfe00..1c21ca0586 100644
--- a/src/net/spdy/spdy_proxy_client_socket.cc
+++ b/src/net/spdy/spdy_proxy_client_socket.cc
@@ -554,6 +554,12 @@ int SpdyProxyClientSocket::DoReadReplyComplete(int result) {
   if (result < 0)
     return result;
 
+  // SpdyHeadersToHttpResponse() may have failed to convert the response
+  // headers (e.g. duplicate location values), in which case
+  // response_.headers is null and must not be dereferenced.
+  if (!response_.headers)
+    return ERR_TUNNEL_CONNECTION_FAILED;
+
   // Require the "HTTP/1.x" status line for SSL CONNECT.
   if (response_.headers->GetHttpVersion() < HttpVersion(1, 0))
     return ERR_TUNNEL_CONNECTION_FAILED;