diff --git a/cabal.project b/cabal.project
index 200c618511..4baba9bca0 100644
--- a/cabal.project
+++ b/cabal.project
@@ -28,10 +28,6 @@ package cryptonite
   -- generation is dubious. Set the flag so we use /dev/urandom by default.
   flags: -support_rdrand
 
-constraints:
-  -- io-classes-mtl-0.1.2.0 is not buildable
-  io-classes-mtl < 0.1.2.0
-
 tests: True
 
 test-show-details: direct