diff --git a/README.md b/README.md
index c7f0cefd064c1f78da57f6928e53ae3c7d2a2f8b..1bd1db68a3765b13c42dd6b43ba95f580a348edb 100644
--- a/README.md
+++ b/README.md
@@ -372,13 +372,15 @@ class App extends Component {
           my_custom_data_1: 'my_custom_field_value_1',
           my_custom_data_2: 'my_custom_field_value_2'
         });
-
-        FCM.deleteInstanceId().then(()={
-          //Deleted instance id successfully
-          //This will reset Instance ID and revokes all tokens.
-        }).catch(error =>{
-          //Error while deleting instance id 
-        })
+        
+        FCM.deleteInstanceId()
+            .then( () => {
+              //Deleted instance id successfully
+              //This will reset Instance ID and revokes all tokens.
+            })
+            .catch(error => {
+              //Error while deleting instance id 
+            });
     }
 }
 ```
diff --git a/ios/RNFIRMessaging.m b/ios/RNFIRMessaging.m
index 94cc0bd02e404e5fd318f98c5ef80ed5ac4172d4..f816f4dd3d06ce74d8caa0cfb908cb393f083bbb 100644
--- a/ios/RNFIRMessaging.m
+++ b/ios/RNFIRMessaging.m
@@ -236,9 +236,9 @@ RCT_EXPORT_METHOD(deleteInstanceId:(RCTPromiseResolveBlock)resolve rejecter:(RCT
   [[FIRInstanceID instanceID]deleteIDWithHandler:^(NSError * _Nullable error) {
     
     if (error != nil) {
-      reject([NSString stringWithFormat:@"%ld",error.code],error.localizedDescription,error);
+      reject([NSString stringWithFormat:@"%ld",error.code],error.localizedDescription,nil);
     } else {
-      resolve(NULL);
+      resolve(nil);
     }
   }];
 }