diff --git a/lib/rack/honeypot.rb b/lib/rack/honeypot.rb
index 96c8f56..3793235 100644
--- a/lib/rack/honeypot.rb
+++ b/lib/rack/honeypot.rb
@@ -22,19 +22,25 @@ def call(env)
         @logger.warn("[Rack::Honeypot] Spam bot detected; responded with null") unless @logger.nil?
         null_response
       else
-        status, headers, body = @app.call(env)
-
-        if @always_enabled || honeypot_header_present?(headers)
-          body = insert_honeypot(body)
-          headers = response_headers(headers, body)
+        @status, @headers, @response = @app.call(env)
+        if @headers["Content-Type"] and @headers["Content-Type"].include?("text/html") and (@always_enabled || honeypot_header_present?(@headers))
+          body = insert_honeypot(response_body(@response))
+          @headers.merge("Content-Length" => body.length.to_s)
+          [@status, @headers, [body]]
+        else
+          [@status, @headers, @response]
         end
-
-        [status, headers, body]
       end
     end
 
     private
 
+    def response_body(response)
+      body = response.respond_to?(:body) ? response.body : response
+      body = body.inject("") { |i, a| i << a } if body.respond_to?(:each)
+      body.to_s
+    end
+
     def spambot_submission?(form_hash)
       form_hash && form_hash[@input_name] && form_hash[@input_name] != @input_value
     end
@@ -43,26 +49,16 @@ def honeypot_header_present?(headers)
       header = headers.delete(HONEYPOT_HEADER)
       header && header.index("enabled")
     end
-    
+
     def null_response
       [200, {'Content-Type' => 'text/html', "Content-Length" => "0"}, []]
     end
-    
-    def response_body(response)
-      body = ""
-
-      # The body may not be an array, so we need to call #each here.
-      response.each {|part| body << part }
 
-      body
-    end
-    
     def response_headers(headers, body)
       headers.merge("Content-Length" => body.length.to_s)
     end
 
     def insert_honeypot(body)
-      body = response_body(body)
       body.gsub!(/<\/head>/, css + "\n</head>")
       body.gsub!(/<form(.*)>/, '<form\1>' + "\n" + div)
       body
diff --git a/rack-honeypot.gemspec b/rack-honeypot.gemspec
index 3e62b4a..dd62e0f 100644
--- a/rack-honeypot.gemspec
+++ b/rack-honeypot.gemspec
@@ -22,5 +22,6 @@ Gem::Specification.new do |s|
 
   s.add_dependency(%q<unindentable>, ["= 0.0.4"])
   s.add_dependency(%q<rack>, [">= 0"])
+  s.add_development_dependency('rack-test')
 end
 
diff --git a/test/test_honeypot.rb b/test/test_honeypot.rb
index f46fe13..d30d386 100644
--- a/test/test_honeypot.rb
+++ b/test/test_honeypot.rb
@@ -1,6 +1,6 @@
 require 'rack/test'
 require 'test/unit'
-require 'mocha'
+require 'mocha/setup'
 require 'unindentable'
 
 require File.expand_path(File.dirname(__FILE__) + '/../lib/rack/honeypot')
@@ -30,7 +30,7 @@ def app
     BLOCK
 
     headers = {
-      'Content-Type'   => 'text/plain',
+      'Content-Type'   => 'text/html',
       'Content-Length' => content.length.to_s,
     }