diff --git a/scripts/e2e/lib/bounded-response-text.mjs b/scripts/e2e/lib/bounded-response-text.mjs
index 70a59816d26..7bb05033fac 100644
--- a/scripts/e2e/lib/bounded-response-text.mjs
+++ b/scripts/e2e/lib/bounded-response-text.mjs
@@ -17,7 +17,7 @@ function parseContentLengthHeader(headers) {
     return undefined;
   }
   const parsed = Number(raw);
-  return Number.isSafeInteger(parsed) ? parsed : undefined;
+  return Number.isSafeInteger(parsed) ? parsed : Number.POSITIVE_INFINITY;
 }
 
 export async function readBoundedResponseText(response, label, byteLimit, timeoutPromise) {
diff --git a/test/scripts/bounded-response-text.test.ts b/test/scripts/bounded-response-text.test.ts
index cc06d818c15..1a4057b76ca 100644
--- a/test/scripts/bounded-response-text.test.ts
+++ b/test/scripts/bounded-response-text.test.ts
@@ -111,4 +111,36 @@ describe("scripts/e2e/lib/bounded-response-text.mjs", () => {
     expect(readStarted).toBe(true);
     expect(canceled).toBe(true);
   });
+
+  it("rejects unsafe decimal content-length values before reading", async () => {
+    let readStarted = false;
+    let canceled = false;
+    const response = {
+      headers: new Headers({ "content-length": "9007199254740993" }),
+      body: {
+        async cancel() {
+          canceled = true;
+        },
+        getReader() {
+          return {
+            async read() {
+              readStarted = true;
+              return new Promise<ReadableStreamReadResult<Uint8Array>>(() => {});
+            },
+            async cancel() {
+              canceled = true;
+            },
+            releaseLock() {},
+          };
+        },
+      },
+    };
+
+    await expect(readBoundedResponseText(response, "probe", 16)).rejects.toMatchObject({
+      code: "ETOOBIG",
+      message: "probe response body exceeded 16 bytes",
+    });
+    expect(readStarted).toBe(false);
+    expect(canceled).toBe(true);
+  });
 });