diff --git a/tox.ini b/tox.ini
index 48d4f5fc..89cbc150 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,7 +5,7 @@ skipsdist = true
 [testenv]
 deps=
     pytest>=2.7.2
-    graphql-core>=1.1
+    graphql-core>=1.1,<2.0
     promise>=2.0
     graphql-relay>=0.4.5
     six