diff --git a/lib/httparty/request.rb b/lib/httparty/request.rb
index 36b7d357..94ffc216 100644
--- a/lib/httparty/request.rb
+++ b/lib/httparty/request.rb
@@ -242,11 +242,8 @@ def setup_raw_request
           force_multipart: options[:multipart]
         )
 
-        if body.multipart?
-          content_type = "multipart/form-data; boundary=#{body.boundary}"
-          @raw_request['Content-Type'] = content_type
-        end
         @raw_request.body = body.call
+        @raw_request['Content-Type'] ||= body.content_type
       end
 
       @raw_request.instance_variable_set(:@decode_content, decompress_content?)
diff --git a/lib/httparty/request/body.rb b/lib/httparty/request/body.rb
index 3fbd7af6..eadf480c 100644
--- a/lib/httparty/request/body.rb
+++ b/lib/httparty/request/body.rb
@@ -16,7 +16,12 @@ def initialize(params, query_string_normalizer: nil, force_multipart: false)
 
       def call
         if params.respond_to?(:to_hash)
-          multipart? ? generate_multipart : normalize_query(params)
+          if multipart?
+            @content_type = "multipart/form-data; boundary=#{boundary}"
+            generate_multipart
+          else
+            normalize_query_and_set_content_type(params)
+          end
         else
           params
         end
@@ -30,6 +35,13 @@ def multipart?
         params.respond_to?(:to_hash) && (force_multipart || has_file?(params))
       end
 
+      def content_type
+        return @content_type if defined?(@content_type)
+        return "multipart/form-data; boundary=#{boundary}" if multipart?
+
+        "application/x-www-form-urlencoded"
+      end
+
       private
 
       # https://html.spec.whatwg.org/#multipart-form-data
@@ -54,7 +66,8 @@ def generate_multipart
           memo << content_body(value)
           memo << NEWLINE.b
         end
-
+        
+        @content_type = "multipart/form-data; boundary=#{boundary}"
         multipart << "--#{boundary}--#{NEWLINE}".b
       end
 
@@ -72,10 +85,12 @@ def file?(object)
         object.respond_to?(:path) && object.respond_to?(:read)
       end
 
-      def normalize_query(query)
+      def normalize_query_and_set_content_type(query)
         if query_string_normalizer
-          query_string_normalizer.call(query)
+          query, @content_type = query_string_normalizer.call(query)
+          query
         else
+          @content_type = 'application/x-www-form-urlencoded'
           HashConversions.to_params(query)
         end
       end
@@ -91,8 +106,9 @@ def content_body(object)
         end
       end
 
-      def content_type(object)
+      def object_content_type(object)
         return object.content_type if object.respond_to?(:content_type)
+        
         require 'mini_mime'
         mime = MiniMime.lookup_by_filename(object.path)
         mime ? mime.content_type : 'application/octet-stream'