diff --git a/lib/zero/response.rb b/lib/zero/response.rb
index 13a053e..22c718b 100644
--- a/lib/zero/response.rb
+++ b/lib/zero/response.rb
@@ -40,7 +40,7 @@ module Zero
         # Set content length, if not already set
         content_length unless header.has_key? 'Content-Length'
         # Set content type, if not already set
-        content_type 'text/html' unless header.has_key? 'Content-Type'
+        self.content_type = 'text/html' unless header.has_key? 'Content-Type'
       end
 
       [status, header, body]
@@ -56,7 +56,7 @@ module Zero
     # Sets the content type to the given value
     # Also creates it, if it does not exists
     #
-    def content_type(value)
+    def content_type=(value)
       self.header['Content-Type'] = value
     end
 
diff --git a/spec/unit/response/response_spec.rb b/spec/unit/response/response_spec.rb
index 4b94dbe..59358c0 100644
--- a/spec/unit/response/response_spec.rb
+++ b/spec/unit/response/response_spec.rb
@@ -48,7 +48,7 @@ describe Zero::Response do
 
     it "removes Content-Type, Content-Length and body on status code 204" do
       subject.body.push '"foobar"'
-      subject.content_type 'application/json'
+      subject.content_type = 'application/json'
       subject.header['Content-Length'] = 8
 
       subject.status = 204
@@ -59,7 +59,7 @@ describe Zero::Response do
 
     it "removes Content-Type, Content-Length and body on status code 304" do
       subject.body.push '"foobar"'
-      subject.content_type 'application/json'
+      subject.content_type = 'application/json'
       subject.header['Content-Length'] = 8
 
       subject.status = 304
@@ -119,7 +119,7 @@ describe Zero::Response do
 
   describe '#content_type' do
     it "sets the Content-Type to the given value" do
-      subject.content_type 'application/json'
+      subject.content_type = 'application/json'
 
       subject.header['Content-Type'].should eq('application/json')
     end