diff --git a/lib/mock/mock-interceptor.js b/lib/mock/mock-interceptor.js
index 781e477502a..1772f0e424f 100644
--- a/lib/mock/mock-interceptor.js
+++ b/lib/mock/mock-interceptor.js
@@ -106,7 +106,7 @@ class MockInterceptor {
     if (typeof data === 'undefined') {
       throw new InvalidArgumentError('data must be defined')
     }
-    if (typeof responseOptions !== 'object') {
+    if (typeof responseOptions !== 'object' || responseOptions === null) {
       throw new InvalidArgumentError('responseOptions must be an object')
     }
   }
diff --git a/test/mock-interceptor.js b/test/mock-interceptor.js
index 036ea69df98..961a7576dc1 100644
--- a/test/mock-interceptor.js
+++ b/test/mock-interceptor.js
@@ -53,7 +53,7 @@ describe('MockInterceptor - reply callback', () => {
   })
 
   test('should error if passed options invalid', t => {
-    t = tspl(t, { plan: 2 })
+    t = tspl(t, { plan: 3 })
 
     const mockInterceptor = new MockInterceptor({
       path: '',
@@ -61,6 +61,7 @@ describe('MockInterceptor - reply callback', () => {
     }, [])
     t.throws(() => mockInterceptor.reply(), new InvalidArgumentError('statusCode must be defined'))
     t.throws(() => mockInterceptor.reply(200, () => { }, 'hello'), new InvalidArgumentError('responseOptions must be an object'))
+    t.throws(() => mockInterceptor.reply(200, () => { }, null), new InvalidArgumentError('responseOptions must be an object'))
   })
 })