diff --git a/src/backend/electron/manager/engineInfoManager.ts b/src/backend/electron/manager/engineInfoManager.ts
index 82147b314c..93b5b929a6 100644
--- a/src/backend/electron/manager/engineInfoManager.ts
+++ b/src/backend/electron/manager/engineInfoManager.ts
@@ -15,7 +15,6 @@ import {
   minimumEngineManifestSchema,
 } from "@/type/preload";
 import { AltPortInfos } from "@/store/type";
-import { UnreachableError } from "@/type/utility";
 import { loadEnvEngineInfos } from "@/domain/defaultEngine/envEngineInfo";
 import { failure, Result, success } from "@/type/result";
 
@@ -47,11 +46,10 @@ export class EngineInfoManager {
         JSON.parse(fs.readFileSync(manifestPath, { encoding: "utf8" })),
       );
     } catch (e) {
-      if (e instanceof Error) {
-        return failure("manifestParseError", e);
-      } else {
-        throw new UnreachableError();
-      }
+      return failure(
+        "manifestParseError",
+        e instanceof Error ? e : new Error("manifest parse error"),
+      );
     }
 
     const [command, ...args] = shlex.split(manifest.command);