--- a/services/common/rest.js
+++ b/services/common/rest.js
@@ -600,16 +600,20 @@ RESTRequest.prototype = {
                     newChannel.URI.spec + ", internal = " + isInternal);
     return isInternal && isSameURI;
   },
 
   /*** nsIChannelEventSink ***/
   asyncOnChannelRedirect:
     function asyncOnChannelRedirect(oldChannel, newChannel, flags, callback) {
 
+    let oldSpec = (oldChannel && oldChannel.URI) ? oldChannel.URI.spec : "<undefined>";
+    let newSpec = (newChannel && newChannel.URI) ? newChannel.URI.spec : "<undefined>";
+    this._log.debug("Channel redirect: " + oldSpec + ", " + newSpec + ", " + flags);
+
     try {
       newChannel.QueryInterface(Ci.nsIHttpChannel);
     } catch (ex) {
       this._log.error("Unexpected error: channel not nsIHttpChannel!");
       callback.onRedirectVerifyCallback(Cr.NS_ERROR_NO_INTERFACE);
       return;
     }