diff --git a/pkg/ruler/notifier.go b/pkg/ruler/notifier.go
index f71391baef..68f44656b6 100644
--- a/pkg/ruler/notifier.go
+++ b/pkg/ruler/notifier.go
@@ -117,7 +117,7 @@ func buildNotifierConfig(rulerConfig *Config) (*config.Config, error) {
 		}
 	}
 	amConfig := &config.AlertmanagerConfig{
-		APIVersion:             config.AlertmanagerAPIVersionV2,
+		APIVersion:             config.AlertmanagerAPIVersionV1,
 		Scheme:                 u.Scheme,
 		PathPrefix:             u.Path,
 		Timeout:                model.Duration(rulerConfig.NotificationTimeout),