diff --git a/src/utils.js b/src/utils.js
index 8be6d72..14ef98a 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -115,37 +115,39 @@ function purgeIfReplyOnce(mock, handler) {
 
 function settle(resolve, reject, response, delay) {
   if (delay > 0) {
-    setTimeout(function () {
-      settle(resolve, reject, response);
-    }, delay);
+    setTimeout(settle, delay, resolve, reject, response);
     return;
   }
 
-  if (response.config && response.config.validateStatus) {
-    response.config.validateStatus(response.status)
-      ? resolve(response)
-      : reject(
-          createAxiosError(
-            "Request failed with status code " + response.status,
-            response.config,
-            response
-          )
-        );
+  // Support for axios < 0.13
+  if (!rejectWithError && (!response.config || !response.config.validateStatus)) {
+    if (response.status >= 200 && response.status < 300) {
+      resolve(response);
+    } else {
+      reject(response);
+    }
     return;
   }
 
-  // Support for axios < 0.11
-  if (response.status >= 200 && response.status < 300) {
+  if (
+    !response.config.validateStatus ||
+    response.config.validateStatus(response.status)
+  ) {
     resolve(response);
   } else {
-    reject(response);
+    if (!rejectWithError) {
+      return reject(response);
+    }
+
+    reject(createAxiosError(
+      'Request failed with status code ' + response.status,
+      response.config,
+      response
+    ));
   }
 }
 
 function createAxiosError(message, config, response, code) {
-  // Support for axios < 0.13.0
-  if (!rejectWithError) return response;
-
   var error = new Error(message);
   error.isAxiosError = true;
   error.config = config;
diff --git a/test/basics.spec.js b/test/basics.spec.js
index 67b899a..1bf06e0 100644
--- a/test/basics.spec.js
+++ b/test/basics.spec.js
@@ -414,6 +414,15 @@ describe("MockAdapter basics", function () {
     });
   });
 
+  it("supports providing a validateStatus null value", function () {
+    instance.defaults.validateStatus = null;
+    mock.onGet("/foo").reply(500);
+
+    return instance.get("/foo").then(function (response) {
+      expect(response.status).to.equal(500);
+    });
+  });
+
   it("respects validatesStatus when requesting unhandled urls", function () {
     instance.defaults.validateStatus = function () {
       return true;