diff --git a/AFNetworking/AFHTTPClient.h b/AFNetworking/AFHTTPClient.h
index 4bf9662..2969c8c 100644
--- a/AFNetworking/AFHTTPClient.h
+++ b/AFNetworking/AFHTTPClient.h
@@ -113,6 +113,8 @@ typedef enum {
 
 /**
  The `AFHTTPClientParameterEncoding` value corresponding to how parameters are encoded into a request body. This is `AFFormURLParameterEncoding` by default.
+ 
+ @warning Some nested parameter structures, such as a keyed array of hashes containing inconsistent keys (i.e. `@{@"": @[@{@"a" : @(1)}, @{@"b" : @(2)}]}`), cannot be unambiguously represented in query strings. It is strongly recommended that an unambiguous encoding, such as `AFJSONParameterEncoding`, is used when posting complicated or nondeterministic parameter structures.
  */
 @property (nonatomic, assign) AFHTTPClientParameterEncoding parameterEncoding;
 
@@ -461,7 +463,7 @@ typedef enum {
  }
  
  `AFFormURLParameterEncoding`
-    Parameters are encoded into field/key pairs in the URL query string for `GET` `HEAD` and `DELETE` requests, and in the message body otherwise.
+    Parameters are encoded into field/key pairs in the URL query string for `GET` `HEAD` and `DELETE` requests, and in the message body otherwise. Dictionary keys are sorted with the `caseInsensitiveCompare:` selector of their description, in order to mitigate the possibility of ambiguous query strings being generated non-deterministically. See the warning for the `parameterEncoding` property for additional information.
  
  `AFJSONParameterEncoding`
     Parameters are encoded into JSON in the message body.
diff --git a/AFNetworking/AFHTTPClient.m b/AFNetworking/AFHTTPClient.m
index 98c574e..d302478 100644
--- a/AFNetworking/AFHTTPClient.m
+++ b/AFNetworking/AFHTTPClient.m
@@ -146,8 +146,13 @@ NSArray * AFQueryStringPairsFromKeyAndValue(NSString *key, id value) {
     NSMutableArray *mutableQueryStringComponents = [NSMutableArray array];
     
     if([value isKindOfClass:[NSDictionary class]]) {
-        [value enumerateKeysAndObjectsUsingBlock:^(id nestedKey, id nestedValue, BOOL *stop) {
-            [mutableQueryStringComponents addObjectsFromArray:AFQueryStringPairsFromKeyAndValue((key ? [NSString stringWithFormat:@"%@[%@]", key, nestedKey] : nestedKey), nestedValue)];
+        // Sort dictionary keys to ensure consistent ordering in query string, which is important when deserializing potentially ambiguous sequences, such as an array of dictionaries 
+        NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"description" ascending:YES selector:@selector(caseInsensitiveCompare:)];
+        [[[value allKeys] sortedArrayUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]] enumerateObjectsUsingBlock:^(id nestedKey, NSUInteger idx, BOOL *stop) {
+            id nestedValue = [value objectForKey:nestedKey];
+            if (nestedValue) {
+                [mutableQueryStringComponents addObjectsFromArray:AFQueryStringPairsFromKeyAndValue((key ? [NSString stringWithFormat:@"%@[%@]", key, nestedKey] : nestedKey), nestedValue)];
+            }
         }];
     } else if([value isKindOfClass:[NSArray class]]) {
         [value enumerateObjectsUsingBlock:^(id nestedValue, NSUInteger idx, BOOL *stop) {