diff --git a/src/browser/WebSourceMapFetcher.ts b/src/browser/WebSourceMapFetcher.ts
index f5657a77b2..546fd9d97c 100644
--- a/src/browser/WebSourceMapFetcher.ts
+++ b/src/browser/WebSourceMapFetcher.ts
@@ -289,7 +289,9 @@ const fetchFollowingApprovedRedirects = async (
       await response.body?.cancel(signal.reason).catch(() => undefined);
       throw signal.reason;
     }
-    if (response.status < 300 || response.status >= 400)
+    // Location is a redirect target only for the Fetch redirect statuses.
+    // A 304 or another 3xx response must retain its own HTTP failure.
+    if (![301, 302, 303, 307, 308].includes(response.status))
       return { response, fetchedUrl: current };
     const location = response.headers.get("location");
     if (location === null) return { response, fetchedUrl: current };
diff --git a/tests/boundary/browser/webSourceMapHttpStatus.test.ts b/tests/boundary/browser/webSourceMapHttpStatus.test.ts
new file mode 100644
index 0000000000..c4e78d72e7
--- /dev/null
+++ b/tests/boundary/browser/webSourceMapHttpStatus.test.ts
@@ -0,0 +1,89 @@
+import { createServer } from "node:http";
+
+import { expect, it } from "vitest";
+
+import { fetchWebSourceMaps } from "../../../src/browser/WebSourceMapFetcher.js";
+import { analyzeWebBundleInputSchema } from "../../../src/domain/webBundleAnalysis.js";
+
+it("follows only HTTP redirect statuses when a source-map response carries Location", async () => {
+  const calls: string[] = [];
+  const server = createServer((request, response) => {
+    const path = request.url ?? "";
+    calls.push(path);
+    if (path === "/delivered.map") {
+      response.writeHead(200, { "content-type": "application/json" }).end(
+        JSON.stringify({
+          version: 3,
+          names: [],
+          sources: ["original.js"],
+          mappings: "AAAA",
+        }),
+      );
+      return;
+    }
+    response
+      .writeHead(Number(path.slice(1)), { location: "/delivered.map" })
+      .end();
+  });
+  try {
+    await new Promise<void>((resolve, reject) => {
+      server.once("error", reject);
+      server.listen(0, "127.0.0.1", resolve);
+    });
+    const address = server.address();
+    if (address === null || typeof address === "string")
+      throw new TypeError("Expected TCP listener");
+    const origin = `http://127.0.0.1:${String(address.port)}`;
+    const input = analyzeWebBundleInputSchema.parse({
+      cdp_endpoint: "http://127.0.0.1:9222",
+      target_id: "selected-page",
+      allowed_origins: [origin],
+      fetch_source_maps: true,
+    });
+    const failures: unknown[] = [];
+    for (const status of [300, 304, 305, 306, 301, 302, 303, 307, 308]) {
+      calls.length = 0;
+      const url = `${origin}/${String(status)}`;
+      const result = await fetchWebSourceMaps(
+        [
+          {
+            scriptKey: `scr_${"1".repeat(64)}`,
+            declaredUrl: url,
+            fetchUrl: url,
+          },
+        ],
+        input,
+      );
+      const redirect = [301, 302, 303, 307, 308].includes(status);
+      try {
+        expect([...calls]).toEqual(
+          redirect
+            ? [`/${String(status)}`, "/delivered.map"]
+            : [`/${String(status)}`],
+        );
+        expect(result.items[0]?.status).toBe(
+          redirect ? "included" : "fetch_failed",
+        );
+        if (!redirect)
+          expect(result.items[0]?.limitation).toBe(
+            `Source-map server returned HTTP ${String(status)}.`,
+          );
+      } catch (cause) {
+        failures.push(cause);
+      }
+    }
+    if (failures.length > 0)
+      throw new AggregateError(
+        failures,
+        "Nonredirect source-map responses were followed",
+      );
+  } finally {
+    server.closeAllConnections();
+    if (server.listening)
+      await new Promise<void>((resolve, reject) =>
+        server.close((error) =>
+          error === undefined ? resolve() : reject(error),
+        ),
+      );
+  }
+});