diff --git a/tests/mocks.py b/tests/mocks.py
index 5561c5aa..7e82d182 100644
--- a/tests/mocks.py
+++ b/tests/mocks.py
@@ -32,5 +32,5 @@ class MockApiClient(ApiClient):
         response = HTTPResponse(
             request=HTTPRequest(path, verb),
             code=200,
-            headers={'Content-Type': 'application-json'})
+            headers={'Content-Type': 'application/json'})
         return self.adapt_response(response)