@@ -221,9 +221,16 @@ -(id)initWithDictionary:(NSDictionary*)dict error:(NSError**)err
         id jsonValue = [dict valueForKeyPath: jsonKeyPath];
 
         //check for Optional properties
-        if (isNull(jsonValue) && property.isOptional==YES) {
+        if (isNull(jsonValue)) {
             //skip this property, continue with next property
-            continue;
+            if (property.isOptional==YES) continue;
+            
+            //null value for required property
+            NSString* msg = [NSString stringWithFormat:@"Value of required model key %@ is null", property.name];
+            JSONModelError* dataErr = [JSONModelError errorInvalidDataWithMessage:msg];
+            *err = [dataErr errorByPrependingKeyPathComponent:property.name];
+            
+            return nil;
         }
 
         Class jsonValueClass = [jsonValue class];
 
@@ -99,7 +99,7 @@ +(NSString*)contentTypeForRequestString:(NSString*)requestString
     //fetch the charset name from the default string encoding
     NSString* contentType = requestContentType;
 
-    if ([contentType isEqualToString:kContentTypeAutomatic]) {
+    if (requestString.length>0 && [contentType isEqualToString:kContentTypeAutomatic]) {
         //check for "eventual" JSON array or dictionary
         NSString* firstAndLastChar = [NSString stringWithFormat:@"%@%@",
                                       [requestString substringToIndex:1],
 
@@ -45,4 +45,17 @@ -(void)testPropertyMissing
 
 }
 
+-(void)testNullValuesForOptionalProperties
+{
+    NSString* jsonWithNulls = @"{\"notRequredProperty\":null,\"fillerNumber\":1}";
+
+    NSError* err;
+    o = [[OptionalPropModel alloc] initWithString: jsonWithNulls error:&err];
+    STAssertNil(err, [err localizedDescription]);
+    STAssertNotNil(o, @"Could not initialize the model");
+    
+    STAssertTrue(!o.notRequredProperty, @"notRequredProperty' is not nil");
+
+}
+
 @end
@@ -148,4 +148,16 @@ -(void)testForNilInputFromDictionary
     STAssertTrue(err.code == kJSONModelErrorNilInput, @"Wrong error for nil dictionary input");
 }
 
+-(void)testForNullValuesForRequiredProperty
+{
+    JSONModelError* err = nil;
+    NSString* jsonString = @"{\"author\":\"Marin\",\"year\":null}";
+
+    CopyrightModel* cpModel = [[CopyrightModel alloc] initWithString:jsonString
+                                                                   error:&err];
+    cpModel = nil;
+    STAssertTrue(err, @"No error returned when initialized with nil dictionary");
+    STAssertTrue(err.code == kJSONModelErrorInvalidData, @"Wrong error null value for a required property");
+}
+
 @end
@@ -11,7 +11,7 @@
 @interface GitHubKeyMapRepoModel : JSONModel
 
 @property (strong, nonatomic) NSString* __description;
-@property (strong, nonatomic) NSString* language;
+@property (strong, nonatomic) NSString<Optional>* language;
 @property (assign, nonatomic) NSString<Index>* name;
 
 @end
@@ -19,7 +19,7 @@
 @property (strong, nonatomic) NSString* owner;
 @property (assign, nonatomic) int forks;
 @property (strong, nonatomic) NSString* description;
-@property (strong, nonatomic) NSString* language;
+@property (strong, nonatomic) NSString<Optional>* language;
 @property (assign, nonatomic) BOOL fork;
 @property (assign, nonatomic) double size;
 @property (assign, nonatomic) int followers;
 
@@ -35,6 +35,6 @@
 @property (strong, nonatomic) NSMutableDictionary* dynamicDictionary;
 
 /* null */
-@property (strong, nonatomic) NSString* notAvailable;
+@property (strong, nonatomic) NSString<Optional>* notAvailable;
 
 @end