diff --git a/setup.py b/setup.py
index cad62d3f..bd085a78 100644
--- a/setup.py
+++ b/setup.py
@@ -26,7 +26,7 @@
     packages=find_packages(include=["gql*"]),
     install_requires=[
         'six>=1.10.0',
-        'graphql-core>=0.5.0',
+        'graphql-core>=0.5.0,<2',
         'promise>=0.4.0'
     ],
     tests_require=['pytest>=2.7.2', 'mock'],