diff --git a/MatrixSDK/JSONModels/MXJSONModel.m b/MatrixSDK/JSONModels/MXJSONModel.m
index 6f3f5423b9..b192f4cc3b 100644
--- a/MatrixSDK/JSONModels/MXJSONModel.m
+++ b/MatrixSDK/JSONModels/MXJSONModel.m
@@ -21,23 +21,43 @@ @implementation MXJSONModel
     NSMutableDictionary *others;
 }
 
-+ (NSDictionary *)JSONKeyPathsByPropertyKey
-{
-    NSMutableDictionary *JSONKeyPathsByPropertyKey = [NSMutableDictionary dictionary];
-    
-    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(?<=[a-z])([A-Z])|([A-Z])(?=[a-z])" options:0 error:nil];
+/**
+ * The JSONKeyPathsByPropertyKey dictionnaries for all subclasses of MXJSONModel.
+ * The key is the child class name. The value, the JSONKeyPathsByPropertyKey dictionnary of the child class.
+ */
+static NSMutableDictionary *JSONKeyPathsByPropertyKeyByClass;
 
-    // List all properties defined by the class
-    NSSet *propertyKeys = [self.class propertyKeys];
-    for (NSString *propertyKey in propertyKeys)
++ (void)initialize
+{
+    @synchronized(JSONKeyPathsByPropertyKeyByClass)
     {
-        // Manage camel-cased properties
-        // Home server uses underscore-separated compounds keys like "event_id". ObjC properties name trend is more camelCase like "eventId".
-        NSString *underscoredString = [[regex stringByReplacingMatchesInString:propertyKey options:0 range:NSMakeRange(0, propertyKey.length) withTemplate:@"_$1$2"] lowercaseString];
-        JSONKeyPathsByPropertyKey[propertyKey] = underscoredString;
+        if (!JSONKeyPathsByPropertyKeyByClass)
+        {
+            JSONKeyPathsByPropertyKeyByClass = [NSMutableDictionary dictionary];
+        }
+
+        // Compute the JSONKeyPathsByPropertyKey for this subclass
+        NSMutableDictionary *JSONKeyPathsByPropertyKey = [NSMutableDictionary dictionary];
+
+        NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(?<=[a-z])([A-Z])|([A-Z])(?=[a-z])" options:0 error:nil];
+
+        // List all properties defined by the class
+        NSSet *propertyKeys = [self.class propertyKeys];
+        for (NSString *propertyKey in propertyKeys)
+        {
+            // Manage camel-cased properties
+            // Home server uses underscore-separated compounds keys like "event_id". ObjC properties name trend is more camelCase like "eventId".
+            NSString *underscoredString = [[regex stringByReplacingMatchesInString:propertyKey options:0 range:NSMakeRange(0, propertyKey.length) withTemplate:@"_$1$2"] lowercaseString];
+            JSONKeyPathsByPropertyKey[propertyKey] = underscoredString;
+        }
+
+        JSONKeyPathsByPropertyKeyByClass[NSStringFromClass(self.class)] = JSONKeyPathsByPropertyKey;
     }
+}
 
-    return JSONKeyPathsByPropertyKey;
++ (NSDictionary *)JSONKeyPathsByPropertyKey
+{
+    return JSONKeyPathsByPropertyKeyByClass[NSStringFromClass(self.class)];
 }
 
 + (id)modelFromJSON:(NSDictionary *)JSONDictionary
diff --git a/MatrixSDK/Utils/MXHTTPClient.m b/MatrixSDK/Utils/MXHTTPClient.m
index 079fa818f5..ec535394b0 100644
--- a/MatrixSDK/Utils/MXHTTPClient.m
+++ b/MatrixSDK/Utils/MXHTTPClient.m
@@ -189,9 +189,13 @@ - (void)tryRequest:(MXHTTPOperation*)mxHTTPOperation
     mxHTTPOperation.numberOfTries++;
     mxHTTPOperation.operation = [httpManager HTTPRequestOperationWithRequest:request success:^(AFHTTPRequestOperation *operation, NSDictionary *JSONResponse) {
 
+        mxHTTPOperation.operation = nil;
         success(JSONResponse);
-        
+
     } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
+
+        mxHTTPOperation.operation = nil;
+
 #if DEBUG
         NSLog(@"[MXHTTPClient] Request %p failed for path: %@ - HTTP code: %ld", mxHTTPOperation, path, (long)operation.response.statusCode);
 #else