diff --git a/internal/model/tempname_test.go b/internal/model/tempname_test.go
new file mode 100644
index 00000000..80639304
--- /dev/null
+++ b/internal/model/tempname_test.go
@@ -0,0 +1,26 @@
+// Copyright (C) 2015 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package model
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestLongTempFilename(t *testing.T) {
+	filename := ""
+	for i := 0; i < 300; i++ {
+		filename += "l"
+	}
+	tFile := defTempNamer.TempName(filename)
+	if len(tFile) < 10 || len(tFile) > 200 {
+		t.Fatal("Invalid long filename")
+	}
+	if !strings.HasSuffix(defTempNamer.TempName("short"), "short.tmp") {
+		t.Fatal("Invalid short filename", defTempNamer.TempName("short"))
+	}
+}