diff --git a/lib/rack/request.rb b/lib/rack/request.rb
index e6e46e9d1..7bd361f00 100644
--- a/lib/rack/request.rb
+++ b/lib/rack/request.rb
@@ -199,28 +199,27 @@ def GET
     # This method support both application/x-www-form-urlencoded and
     # multipart/form-data.
     def POST
-      if @env["rack.input"].nil?
-        raise "Missing rack.input"
-      elsif @env["rack.request.form_input"].equal? @env["rack.input"]
-        @env["rack.request.form_hash"]
-      elsif form_data? || parseable_data?
-        unless @env["rack.request.form_hash"] = parse_multipart(env)
+      raise "Missing rack.input" if @env["rack.input"].nil?
+      @env["rack.request.form_hash"] ||= {}
+
+      if !(@env["rack.request.form_input"].equal? @env["rack.input"]) && (form_data? || parseable_data?)
+        parsed_result = parse_multipart(env)
+        if parsed_result
+          @env["rack.request.form_hash"].merge! parsed_result
+        else
           form_vars = @env["rack.input"].read
-
           # Fix for Safari Ajax postings that always append \0
           # form_vars.sub!(/\0\z/, '') # performance replacement:
           form_vars.slice!(-1) if form_vars[-1] == ?\0
 
           @env["rack.request.form_vars"] = form_vars
-          @env["rack.request.form_hash"] = parse_query(form_vars)
-
+          @env["rack.request.form_hash"].merge! parse_query(form_vars)
           @env["rack.input"].rewind
         end
         @env["rack.request.form_input"] = @env["rack.input"]
-        @env["rack.request.form_hash"]
-      else
-        {}
       end
+
+      @env["rack.request.form_hash"]
     end
 
     # The union of GET and POST data.