@@ -211,7 +211,7 @@ -(BOOL)__doesDictionary:(NSDictionary*)dict matchModelWithKeyMapper:(JSONKeyMapp
 {
     //check if all required properties are present
     NSArray* incomingKeysArray = [dict allKeys];
-    NSMutableSet* requiredProperties = [self __requiredPropertyNames];
+    NSMutableSet* requiredProperties = [self __requiredPropertyNames].mutableCopy;
     NSSet* incomingKeys = [NSSet setWithArray: incomingKeysArray];
 
     //transform the key names, if neccessary
Original file line number	Diff line number	Diff line change
`@@ -211,7 +211,7 @@ -(BOOL)__doesDictionary:(NSDictionary*)dict matchModelWithKeyMapper:(JSONKeyMapp`
`211`	`211`	`{`
`212`	`212`	`//check if all required properties are present`
`213`	`213`	`NSArray* incomingKeysArray = [dict allKeys];`
`214`		`- NSMutableSet* requiredProperties = [self __requiredPropertyNames];`
	`214`	`+ NSMutableSet* requiredProperties = [self __requiredPropertyNames].mutableCopy;`
`215`	`215`	`NSSet* incomingKeys = [NSSet setWithArray: incomingKeysArray];`
`216`	`216`
`217`	`217`	`//transform the key names, if neccessary`