diff --git a/servant-mock/servant-mock.cabal b/servant-mock/servant-mock.cabal
index 31acbed7..e7d70b15 100644
--- a/servant-mock/servant-mock.cabal
+++ b/servant-mock/servant-mock.cabal
@@ -30,7 +30,7 @@ library
     http-types >= 0.8 && <0.9,
     servant >= 0.4,
     servant-server >= 0.4,
-    transformers >= 0.4 && <0.5,
+    transformers >= 0.3 && <0.5,
     QuickCheck >= 2.8 && <2.9,
     wai >= 3.0 && <3.1
   hs-source-dirs:      src