diff --git a/Rexxar/Decorator/RXRRequestDecorator.m b/Rexxar/Decorator/RXRRequestDecorator.m
index f3ab2e8..69c2f2b 100644
--- a/Rexxar/Decorator/RXRRequestDecorator.m
+++ b/Rexxar/Decorator/RXRRequestDecorator.m
@@ -11,8 +11,19 @@
 
 #import "NSURL+Rexxar.h"
 
+@interface RXRRequestDecorator ()
+
+@property (nonatomic, strong) RXRHTTPRequestSerializer *requestSerializer;
+
+@end
+
 @implementation RXRRequestDecorator
 
+- (instancetype)init
+{
+  return [self initWithHeaders:@{} parameters:@{}];
+}
+
 - (instancetype)initWithHeaders:(NSDictionary *)headers
                      parameters:(NSDictionary *)parameters
 {
@@ -20,6 +31,14 @@ - (instancetype)initWithHeaders:(NSDictionary *)headers
   if (self) {
     _headers = [headers copy];
     _parameters = [parameters copy];
+    _requestSerializer = [[RXRHTTPRequestSerializer alloc] init];
+
+    // Do not encode queries to HTTP body for POST method.
+    if (![_requestSerializer.HTTPMethodsEncodingParametersInURI containsObject:@"POST"]) {
+      NSMutableSet *set = [_requestSerializer.HTTPMethodsEncodingParametersInURI mutableCopy];
+      [set addObject:@"POST"];
+      _requestSerializer.HTTPMethodsEncodingParametersInURI = [set copy];
+    }
   }
   return self;
 }
@@ -48,24 +67,16 @@ - (NSURLRequest *)decoratedRequestFromOriginalRequest:(NSURLRequest *)originalRe
   NSMutableDictionary *parameters = [NSMutableDictionary dictionaryWithDictionary:self.parameters];
   [self _rxr_addQuery:mutableRequest.URL.query toParameters:parameters];
 
-  // Get parameters from POST request body
-  // Note: `requestBySerializingRequest:withParameters:error:` method will add query to HTTP body for POST request
-  if ([mutableRequest.HTTPMethod.uppercaseString isEqualToString:@"POST"]
-      && mutableRequest.HTTPBody
-      && [[[mutableRequest valueForHTTPHeaderField:@"Content-Type"] lowercaseString] isEqualToString:@"application/x-www-form-urlencoded"]) {
-    NSString *bodyQueries = [[NSString alloc] initWithData:mutableRequest.HTTPBody encoding:kCFStringEncodingUTF8];
-    [self _rxr_addQuery:bodyQueries toParameters:parameters];
-  }
-
-  // Remove query from url because RXRHTTPRequestSerializer will add all the parameters through
-  // `requestBySerializingRequest:withParameters:error:` method.
+  // Note: mutableRequest.URL.query has been added to the paramters, _requestSerializer will generate a new NSURLRequest
+  // object from the parameters every time when it decorates a request. If we don't remove query from URL, request may
+  // contain duplicated query string if the original request is decorated more than 2 times.
   NSURLComponents *comp = [[NSURLComponents alloc] initWithURL:mutableRequest.URL resolvingAgainstBaseURL:NO];
   comp.query = nil;
   mutableRequest.URL = comp.URL;
 
-  return [[RXRHTTPRequestSerializer serializer] requestBySerializingRequest:[mutableRequest copy]
-                                                             withParameters:parameters
-                                                                      error:nil];
+  return [_requestSerializer requestBySerializingRequest:mutableRequest
+                                          withParameters:parameters
+                                                   error:nil];
 }
 
 - (void)_rxr_addQuery:(NSString *)query toParameters:(NSMutableDictionary *)parameters