diff --git a/pkg/api/preferences.go b/pkg/api/preferences.go
index 55c0535477e..b9626f49831 100644
--- a/pkg/api/preferences.go
+++ b/pkg/api/preferences.go
@@ -128,7 +128,7 @@ func (hs *HTTPServer) UpdateUserPreferences(c *contextmodel.ReqContext) response
 }
 
 func (hs *HTTPServer) updatePreferencesFor(ctx context.Context, orgID, userID, teamId int64, dtoCmd *dtos.UpdatePrefsCmd) response.Response {
-	if !pref.IsValidThemeID(dtoCmd.Theme) {
+	if dtoCmd.Theme != "" && !pref.IsValidThemeID(dtoCmd.Theme) {
 		return response.Error(http.StatusBadRequest, "Invalid theme", nil)
 	}