diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+# 0.5.0.0
+
+- Removed the `NoThunks` instance for `NonNullMap`, and the dependency on
+  `nothunks`. The `monoidmap` package no longer relies on this instance.
+
 # 0.4.0.0
 
 - Revised the module structure of the package, replacing the
diff --git a/components/monoidmap-internal/Data/MonoidMap/Internal/NonNullMap/Unsafe.hs b/components/monoidmap-internal/Data/MonoidMap/Internal/NonNullMap/Unsafe.hs
--- a/components/monoidmap-internal/Data/MonoidMap/Internal/NonNullMap/Unsafe.hs
+++ b/components/monoidmap-internal/Data/MonoidMap/Internal/NonNullMap/Unsafe.hs
@@ -28,8 +28,6 @@
     ( Map )
 import Data.MonoidMap.Internal.NonNull.Unsafe
     ( NonNull (UnsafeNonNull) )
-import NoThunks.Class
-    ( NoThunks )
 
 -- | A map of 'NonNull' values.
 --
@@ -47,7 +45,7 @@
     -- For example, the 'Read' instance for 'Map', given appropriate input,
     -- will quite happily produce maps with 'mempty' values.
     --
-    deriving (Eq, Show, NFData, NoThunks) via Map k v
+    deriving (Eq, Show, NFData) via Map k v
     deriving (Eq1, Show1, Foldable) via Map k
     deriving (Eq2, Show2, Bifoldable) via Map
 
diff --git a/monoidmap-internal.cabal b/monoidmap-internal.cabal
--- a/monoidmap-internal.cabal
+++ b/monoidmap-internal.cabal
@@ -1,6 +1,6 @@
 cabal-version:  3.0
 name:           monoidmap-internal
-version:        0.4.0.0
+version:        0.5.0.0
 homepage:       https://github.com/jonathanknowles/monoidmap/tree/HEAD/packages/monoidmap-internal
 bug-reports:    https://github.com/jonathanknowles/monoidmap/issues
 license:        Apache-2.0
@@ -24,8 +24,6 @@
     build-depends:deepseq                       >= 1.4.4.0    && < 1.6
 common dependency-monoid-subclasses
     build-depends:monoid-subclasses             >= 1.2.3      && < 1.3
-common dependency-nothunks
-    build-depends:nothunks                      >= 0.1.3      && < 0.4
 common dependency-tasty-bench
     build-depends:tasty-bench                   >= 0.3.2      && < 0.6
 
@@ -60,7 +58,6 @@
       , dependency-containers
       , dependency-deepseq
       , dependency-monoid-subclasses
-      , dependency-nothunks
       , extensions
     hs-source-dirs:
         components/monoidmap-internal