diff --git a/frontend/tests/util/isolation.ts b/frontend/tests/util/isolation.ts
index ac99411f3..da14598c3 100644
--- a/frontend/tests/util/isolation.ts
+++ b/frontend/tests/util/isolation.ts
@@ -61,6 +61,10 @@ export const test = base.extend<CustomTestFixtures, CustomWorkerFixtures>({
             ["serve", "--config", configPath],
             // { stdio: "inherit" }
         );
+        tobiraProcess.addListener("exit", code => {
+            throw new Error(`Failed to start Tobira process (exit code ${code}). `
+                + 'Invalid config? (Hint: try setting stdio: "inherit" in isolation.ts)');
+        });
         await waitPort({ port, interval: 10, output: "silent" });