diff --git a/TIASshot/SelfTest/SelfTestRunner.cs b/TIASshot/SelfTest/SelfTestRunner.cs
index 39dbc15..00c11ef 100644
--- a/TIASshot/SelfTest/SelfTestRunner.cs
+++ b/TIASshot/SelfTest/SelfTestRunner.cs
@@ -77,11 +77,13 @@
             var stamp = $"{DateTime.Now:yyyyMMdd-HHmmss}-{Process.GetCurrentProcess().Id}";
             var tempRoot = Path.Combine(Path.GetTempPath(), "TIASshot-selftest");
             var workDir = Path.Combine(tempRoot, $"work-{stamp}");
-            var outPath = Path.GetFullPath(GetArgValue(args, FlagOut) ?? Path.Combine(tempRoot, $"result-{stamp}.txt"));
+            var outPath = GetArgValue(args, FlagOut) ?? Path.Combine(tempRoot, $"result-{stamp}.txt");
             var keep = HasFlag(args, FlagKeep);
 
             SelfTestReport report;
             try {
+                // 不正な --selftest-out（空文字・不正文字等）も結果ファイルを作成できない場合と同じく異常（2）とする
+                outPath = Path.GetFullPath(outPath);
                 report = new SelfTestReport(outPath);
             } catch (Exception ex) {
                 Debug.WriteLine($"セルフテスト結果ファイルを作成できません: {outPath}: {ex}");