diff --git a/server/upstream/upstream.go b/server/upstream/upstream.go
index 292e7d3..42e6697 100644
--- a/server/upstream/upstream.go
+++ b/server/upstream/upstream.go
@@ -79,9 +79,11 @@ func (o *Options) Upstream(ctx *context.Context, giteaClient *gitea.Client) (fin
 		if ifModifiedSince, err := time.Parse(time.RFC1123, string(ctx.Response().Header.Get(headerIfModifiedSince))); err == nil {
 			if !ifModifiedSince.Before(o.BranchTimestamp) {
 				ctx.RespWriter.WriteHeader(http.StatusNotModified)
+				log.Trace().Msg("check response against last modified: valid")
 				return true
 			}
 		}
+		log.Trace().Msg("check response against last modified: outdated")
 	}
 
 	log.Debug().Msg("Preparing")