diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## [0.1.0.1] - 2026-07-29
+
+* Test-only: a regression test for the manifest `.txt` encoding fix in
+  `sydtest-mutation-runtime` 0.1.1.0, which the test suite now requires.  The
+  library is unchanged.
+
 ## [0.1.0.0] - 2026-07-16
 
 * First released version.
diff --git a/Setup.hs b/Setup.hs
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/sydtest-mutation.cabal b/sydtest-mutation.cabal
--- a/sydtest-mutation.cabal
+++ b/sydtest-mutation.cabal
@@ -5,7 +5,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           sydtest-mutation
-version:        0.1.0.0
+version:        0.1.0.1
 synopsis:       Mutation testing for sydtest
 description:    Mutation testing for sydtest test suites. It builds on the sydtest test framework to introduce mutations into code under test and report which mutations the test suite fails to catch. See https://github.com/NorfairKing/sydtest#readme for more information.
 category:       Testing
@@ -46,6 +46,7 @@
   other-modules:
       Test.Syd.AugmentedManifestSpec
       Test.Syd.CoverageBaselineSpec
+      Test.Syd.ManifestRenderSpec
       Test.Syd.ManifestSpec
       Test.Syd.MutationIdSpec
       Test.Syd.MutationSpec
@@ -69,8 +70,9 @@
     , genvalidity-sydtest-aeson
     , path
     , path-io
+    , safe-coloured-text
     , sydtest
     , sydtest-mutation
-    , sydtest-mutation-runtime
+    , sydtest-mutation-runtime >=0.1.1
     , text
   default-language: Haskell2010
diff --git a/test/Test/Syd/ManifestRenderSpec.hs b/test/Test/Syd/ManifestRenderSpec.hs
new file mode 100644
--- /dev/null
+++ b/test/Test/Syd/ManifestRenderSpec.hs
@@ -0,0 +1,24 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE QuasiQuotes #-}
+
+module Test.Syd.ManifestRenderSpec (spec) where
+
+import qualified Data.ByteString as SB
+import qualified Data.Text.Encoding as TE
+import Path
+import Path.IO (withSystemTempDir)
+import Test.Syd
+import Test.Syd.Mutation.Manifest.Render (renderManifest, writeManifestTxtFile)
+import Test.Syd.Validity
+import Text.Colour
+
+spec :: Spec
+spec =
+  describe "writeManifestTxtFile" $
+    it "writes exactly the rendered manifest, encoded as UTF-8" $
+      forAllValid $ \manifest ->
+        withSystemTempDir "sydtest-mutation-manifest-txt" $ \dir -> do
+          writeManifestTxtFile dir "Example.Mod" manifest
+          contents <- SB.readFile (fromAbsFile (dir </> [relfile|Example.Mod.txt|]))
+          TE.decodeUtf8' contents
+            `shouldBe` Right (renderChunksText With8BitColours (unlinesChunks (renderManifest "Example.Mod" manifest)))