diff --git a/webserver.go b/webserver.go
index ac9610b..59b8e7e 100644
--- a/webserver.go
+++ b/webserver.go
@@ -144,7 +144,7 @@ func groupHandler(w http.ResponseWriter, r *http.Request) {
 		if os.IsNotExist(err) {
 			notFound(w)
 		} else {
-			log.Println("addGroup: %v", err)
+			log.Printf("addGroup: %v", err)
 			http.Error(w, "Internal server error",
 				http.StatusInternalServerError)
 		}