diff --git a/simple-log.cabal b/simple-log.cabal
--- a/simple-log.cabal
+++ b/simple-log.cabal
@@ -1,5 +1,5 @@
 Name:                 simple-log
-Version:              0.9.1
+Version:              0.9.2
 Synopsis:             Simple log for Haskell
 Description:          Log library for Haskell
 License:              BSD3
@@ -31,7 +31,7 @@
     hformat == 0.3.*,
     microlens == 0.4.*,
     microlens-platform == 0.3.*,
-    mmorph == 1.0.*,
+    mmorph >= 1.0 && < 1.2,
     mtl >= 2.2 && < 2.3,
     SafeSemaphore >= 0.9.0 && < 1.0.0,
     text >= 0.11.0 && < 2.0.0,