diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -1,3 +1,7 @@
+0.11.1 [2019.08.27]
+-------------------
+* Make `Data.Constraint.Deferrable.UnsatisfiedConstraint` a newtype.
+
 0.11 [2019.05.10]
 -----------------
 * Introduce a `HasDict` type class for types that witness evidence of
diff --git a/constraints.cabal b/constraints.cabal
--- a/constraints.cabal
+++ b/constraints.cabal
@@ -1,6 +1,6 @@
 name:          constraints
 category:      Constraints
-version:       0.11
+version:       0.11.1
 license:       BSD2
 cabal-version: >= 1.10
 license-file:  LICENSE
diff --git a/src/Data/Constraint/Deferrable.hs b/src/Data/Constraint/Deferrable.hs
--- a/src/Data/Constraint/Deferrable.hs
+++ b/src/Data/Constraint/Deferrable.hs
@@ -55,7 +55,7 @@
 import Data.Type.Equality ((:~~:)(HRefl))
 #endif
 
-data UnsatisfiedConstraint = UnsatisfiedConstraint String
+newtype UnsatisfiedConstraint = UnsatisfiedConstraint String
   deriving (Typeable, Show)
 
 instance Exception UnsatisfiedConstraint