diff --git a/src/runtime/api/csrf_jsc.rs b/src/runtime/api/csrf_jsc.rs
index ce3fcca122b3..7f9482525a44 100644
--- a/src/runtime/api/csrf_jsc.rs
+++ b/src/runtime/api/csrf_jsc.rs
@@ -21,33 +21,6 @@ fn algorithm_from_js_case_insensitive(
     Ok(evp::lookup_ignore_case(slice.slice()))
 }
 
-/// Validates an optional integer property in `[0, MAX_SAFE_INTEGER]`.
-/// Differs from `JSValue::get_optional_int::<u64>` in rejecting NaN and in
-/// the error message wording expected by existing tests.
-fn get_optional_int_u64(
-    target: JSValue,
-    global: &JSGlobalObject,
-    property: &'static str,
-) -> JsResult<Option<u64>> {
-    let Some(value) = target.get(global, property)? else {
-        return Ok(None);
-    };
-    if value.is_undefined() || value.is_empty() {
-        return Ok(Some(0));
-    }
-    if !value.is_number() {
-        return Err(global.throw_invalid_argument_type_value(property, "number", value));
-    }
-    let num: f64 = value.as_number();
-    const MAX_SAFE_INTEGER: f64 = 9007199254740991.0;
-    if num.fract() != 0.0 || num < 0.0 || num > MAX_SAFE_INTEGER {
-        return Err(global.throw_invalid_arguments(format_args!(
-            "{property} must be an integer between 0 and {MAX_SAFE_INTEGER}"
-        )));
-    }
-    Ok(Some(num as u64))
-}
-
 /// JS binding function for generating CSRF tokens
 /// First argument is secret (required), second is options (optional)
 #[bun_jsc::host_fn]
@@ -81,7 +54,7 @@ pub(crate) fn csrf__generate(global: &JSGlobalObject, frame: &CallFrame) -> JsRe
         let options_value = args[1];
 
         // Extract expiresIn (optional)
-        if let Some(expires_in_js) = get_optional_int_u64(options_value, global, "expiresIn")? {
+        if let Some(expires_in_js) = options_value.get_optional_int::<u64>(global, "expiresIn")? {
             expires_in = expires_in_js;
         }
 
@@ -246,7 +219,7 @@ pub(crate) fn csrf__verify(global: &JSGlobalObject, frame: &CallFrame) -> JsResu
         }
 
         // Extract maxAge (optional)
-        if let Some(max_age_js) = get_optional_int_u64(options_value, global, "maxAge")? {
+        if let Some(max_age_js) = options_value.get_optional_int::<u64>(global, "maxAge")? {
             max_age = max_age_js;
         }
 
diff --git a/test/js/bun/util/csrf.test.ts b/test/js/bun/util/csrf.test.ts
index fedc1279c25d..1cfd7aa2f10f 100644
--- a/test/js/bun/util/csrf.test.ts
+++ b/test/js/bun/util/csrf.test.ts
@@ -160,6 +160,16 @@ describe("Bun.CSRF", () => {
     );
   });
 
+  test("expiresIn and maxAge accept NaN as 0 (no expiry)", () => {
+    // NaN falls through to the integer validator's fallback (0 = no expiry),
+    // matching node's integer validators. Note: this differs from omitting the
+    // option entirely, which defaults to 24h.
+    const token = CSRF.generate(secret, { expiresIn: NaN });
+    expect(typeof token).toBe("string");
+    expect(token.length).toBeGreaterThan(0);
+    expect(CSRF.verify(token, { secret, maxAge: NaN })).toBe(true);
+  });
+
   test("error handling", () => {
     // Empty token
     expect(() => CSRF.verify("", { secret })).toThrow();
@@ -182,6 +192,28 @@ describe("Bun.CSRF", () => {
     expect(() => CSRF.generate(secret, { sessionId: 123 })).toThrow();
     // @ts-expect-error - testing invalid input
     expect(() => CSRF.verify(token, { secret, sessionId: 123 })).toThrow();
+
+    // expiresIn / maxAge validation
+    expect(() => CSRF.generate(secret, { expiresIn: -1 })).toThrow(
+      expect.objectContaining({ code: "ERR_OUT_OF_RANGE" }),
+    );
+    expect(() => CSRF.generate(secret, { expiresIn: 1.5 })).toThrow(
+      expect.objectContaining({ code: "ERR_INVALID_ARG_TYPE" }),
+    );
+    // @ts-expect-error - testing invalid input
+    expect(() => CSRF.generate(secret, { expiresIn: "foo" })).toThrow(
+      expect.objectContaining({ code: "ERR_INVALID_ARG_TYPE" }),
+    );
+    expect(() => CSRF.verify(token, { secret, maxAge: -1 })).toThrow(
+      expect.objectContaining({ code: "ERR_OUT_OF_RANGE" }),
+    );
+    expect(() => CSRF.verify(token, { secret, maxAge: 1.5 })).toThrow(
+      expect.objectContaining({ code: "ERR_INVALID_ARG_TYPE" }),
+    );
+    // @ts-expect-error - testing invalid input
+    expect(() => CSRF.verify(token, { secret, maxAge: "foo" })).toThrow(
+      expect.objectContaining({ code: "ERR_INVALID_ARG_TYPE" }),
+    );
   });
 
   test("handle bad decoding", () => {