diff --git a/lib/mountebank/stub/http_response.rb b/lib/mountebank/stub/http_response.rb
index b0f985d..1759c75 100644
--- a/lib/mountebank/stub/http_response.rb
+++ b/lib/mountebank/stub/http_response.rb
@@ -4,7 +4,7 @@ def self.create(statusCode=200, headers={}, body='', behaviors={}, mode='')
     payload[:statusCode] = statusCode
     payload[:headers] = headers unless headers.empty?
     payload[:body] = body unless body.empty?
-    payload[:_mode] = mode unless mode.empty?
+    payload[:_mode] = mode if (mode == 'text' or mode == 'binary')
 
     data = {is: payload}
     data.merge!(_behaviors: behaviors) unless behaviors.empty?
diff --git a/spec/mountebank/stub/http_response_spec.rb b/spec/mountebank/stub/http_response_spec.rb
index 0917bd3..5f87f30 100644
--- a/spec/mountebank/stub/http_response_spec.rb
+++ b/spec/mountebank/stub/http_response_spec.rb
@@ -22,6 +22,14 @@
       end
     end
 
+    context 'invalid binary mode' do
+        let(:mode) { 'random' }
+        it 'returns response object without binary mode' do
+          expect(response).to be_a Mountebank::Stub::HttpResponse
+          expect(response.to_json).to eq '{"is":{"statusCode":200,"headers":{"Content-Type":"application/json"},"body":"{\"foo\":\"bar\"}"}}'
+        end
+    end
+
     context 'with behaviors' do
         let(:behaviors) { { wait: 10000 } }
       it 'returns a response object' do