diff --git a/chrome/browser/external_protocol/external_protocol_handler.cc b/chrome/browser/external_protocol/external_protocol_handler.cc
index 4095382b8c535dca2258bfead1b0c360a2996826..24a0809ad234767a59315a0c562833b57c7abd88 100644
--- a/chrome/browser/external_protocol/external_protocol_handler.cc
+++ b/chrome/browser/external_protocol/external_protocol_handler.cc
@@ -438,7 +438,7 @@ ExternalProtocolHandler::BlockState ExternalProtocolHandler::GetBlockState(
   if (scheme == "mailto") {
     base::UmaHistogramEnumeration(kBlockStateMetric,
                                   BlockStateMetric::kAllowedDefaultMail);
-    return DONT_BLOCK;
+    return UNKNOWN;
   }
 
   PrefService* profile_prefs = profile->GetPrefs();