diff --git a/metrics_constants.h b/metrics_constants.h
index b3833a3..161d585 100644
--- a/metrics_constants.h
+++ b/metrics_constants.h
@@ -60,6 +60,11 @@
   // above block and before the kInputMalformed field. This
   // is to ensure that error codes are not reordered.
 
+  // This error is reported when libcurl returns CURLE_COULDNT_RESOLVE_HOST and
+  // calling res_init() can recover.
+  kUnresolvedHostRecovered = 97,
+  // This error is reported when libcurl returns CURLE_COULDNT_RESOLVE_HOST.
+  kUnresolvedHost = 98,
   // This error is reported when libcurl has an internal error that
   // update_engine can't recover from.
   kInternalError = 99,