diff --git a/.github/workflows/whitespace.yml b/.github/workflows/whitespace.yml
new file mode 100644
index 0000000..6ac20d3
--- /dev/null
+++ b/.github/workflows/whitespace.yml
@@ -0,0 +1,13 @@
+name: whitespace
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+    - uses: andreasabel/fix-whitespace-action@v1
diff --git a/ALTERNATIVES.md b/ALTERNATIVES.md
index bd28684..2eed463 100644
--- a/ALTERNATIVES.md
+++ b/ALTERNATIVES.md
@@ -44,8 +44,8 @@ ensures correct versions in the freeze file.
 
 ```
 > stack2cabal --help
-Usage: stack2cabal [-f|--file STACK_YAML] [-o|--output-file CABAL_PROJECT] 
-                   [--no-inspect-remotes] [--no-pin-ghc] [--no-sort-repos] 
+Usage: stack2cabal [-f|--file STACK_YAML] [-o|--output-file CABAL_PROJECT]
+                   [--no-inspect-remotes] [--no-pin-ghc] [--no-sort-repos]
                    [--no-run-hpack] [-p|--pin-hackage-index FUZZY_DATE]
 
 Available options:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9ae6833..dc6f7c3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -37,7 +37,7 @@
 
   3 directories, 8 files
 
-  $ cat project-dhall/pkgs/all-in-one.dhall 
+  $ cat project-dhall/pkgs/all-in-one.dhall
   -- NOTE: Using an empty list should trigger warnings like the following:
   --
   -- $ stack build
@@ -60,7 +60,7 @@
   -- There is no <pkgname>.cabal package file or cabal.project file. To build
   -- packages locally you need at minimum a <pkgname>.cabal file. You can use 'cabal
   -- init' to create one.
-  -- 
+  --
   -- For non-trivial projects you will also want a cabal.project file in the root
   -- directory of your project. This file lists the packages in your project and all
   -- other build configuration. See the Cabal user guide for full details.
@@ -71,4 +71,4 @@
   ```
 
 ### 1.0.0
-* First release
\ No newline at end of file
+* First release
diff --git a/HACKING.md b/HACKING.md
index e59ffe5..2b4b1f6 100644
--- a/HACKING.md
+++ b/HACKING.md
@@ -67,4 +67,4 @@ $ ./pkgs-sorted.hs
 , "./docs/"
 , "./testing/"
 ]
-```
\ No newline at end of file
+```
diff --git a/README.md b/README.md
index 2e19f82..ea4e274 100644
--- a/README.md
+++ b/README.md
@@ -365,22 +365,22 @@ UPDO_URL := ${HACKAGE}/updo-${UPDO_VERSION}/updo-${UPDO_VERSION}.tar.gz
 
 ```make
 updo/Makefile:
-	rm -rf updo
-	curl -sSL ${UPDO_URL} | tar -xz
-	mv updo-* updo
-	chmod +x $$(grep -RIl '^#!' updo)
+⇥ rm -rf updo
+⇥ curl -sSL ${UPDO_URL} | tar -xz
+⇥ mv updo-* updo
+⇥ chmod +x $$(grep -RIl '^#!' updo)
 ```
 
 2. When opting to install the included executables:
 
 ```make
 updo/Makefile:
-	rm -rf updo
-	curl -sSL ${UPDO_URL} | tar -xz
-	cd updo-${UPDO_VERSION}
-	stack install
-	cd -
-	mv updo-* updo
+⇥ rm -rf updo
+⇥ curl -sSL ${UPDO_URL} | tar -xz
+⇥ cd updo-${UPDO_VERSION}
+⇥ stack install
+⇥ cd -
+⇥ mv updo-* updo
 ```
 
 Both `cabal get` and `stack unpack` can also unpack package sources from
@@ -397,19 +397,19 @@ UPDO_VERSION ?= 4a8359f4e5d8cad61f35bea9d0a8f04477829ca1
 UPDO_URL := https://github.com/cabalism/updo/archive/${UPDO_VERSION}.tar.gz
 
 updo/Makefile:
-	rm -rf updo
-	curl -sSL ${UPDO_URL} | tar -xz
-	mv updo-* updo
-	chmod +x $$(grep -RIl '^#!' updo)
+⇥ rm -rf updo
+⇥ curl -sSL ${UPDO_URL} | tar -xz
+⇥ mv updo-* updo
+⇥ chmod +x $$(grep -RIl '^#!' updo)
 ```
 
 2. From a branch:
 
 ```make
 updo/Makefile:
-	rm -rf updo
-	git clone --depth=1 --branch main git@github.com:cabalism/updo
-	chmod +x $$(grep -RIl '^#!' updo)
+⇥ rm -rf updo
+⇥ git clone --depth=1 --branch main git@github.com:cabalism/updo
+⇥ chmod +x $$(grep -RIl '^#!' updo)
 ```
 
 # Make Targets
@@ -542,7 +542,7 @@ SHA256MAP_VIA_PYTHON ?= false
 # overriding the recipe for this target.
 ifeq ($(SHA256MAP_VIA_PYTHON), true)
 ghc-$(GHC_VERSION).sha256map.nix: stack.yaml
-	updo/project-nix/sha256map.py <$^ >$@
+⇥ updo/project-nix/sha256map.py <$^ >$@
 endif
 ```
 
diff --git a/TEMPLATES.md b/TEMPLATES.md
index f4229b0..dad4fcf 100644
--- a/TEMPLATES.md
+++ b/TEMPLATES.md
@@ -18,4 +18,4 @@ Available options:
   --file FILE              Read expression from a file instead of standard input
   --output FILE            Write result to a file instead of standard output
   -h,--help                Show this help text
-```
\ No newline at end of file
+```
diff --git a/TESTING.md b/TESTING.md
index 8345aa3..1fd4f48 100644
--- a/TESTING.md
+++ b/TESTING.md
@@ -18,7 +18,7 @@ Assuming this layout of make files in updo and at the root of your project.
 We'll need some versions, something like:
 
 ```
-$ cat project-versions.mk 
+$ cat project-versions.mk
 # Versions of GHC and stackage resolver, the ones we're on and the next ones
 # we're upgrading to.
 GHC_VERSION := 8.10.7
@@ -40,7 +40,7 @@ include project-versions.mk
 include updo/Makefile
 
 project-nix/ghc-%/sha256map.nix: ghc-%.sha256map.nix
-	mkdir -p $(@D) && cp $^ $@
+        mkdir -p $(@D) && cp $^ $@
 
 .PHONY: all
 all: \
@@ -70,9 +70,9 @@ include updo/alternatives/yaml2stack/Makefile
 # overriding the recipe for this target.
 ifeq ($(SHA256MAP_VIA_PYTHON), true)
 ghc-$(GHC_VERSION).sha256map.nix: stack.yaml
-	updo/project-nix/sha256map.py <$^ >$@
+        updo/project-nix/sha256map.py <$^ >$@
 ghc-$(GHC_UPGRADE).sha256map.nix: stack.yaml
-	updo/project-nix/sha256map.py <$^ >$@
+        updo/project-nix/sha256map.py <$^ >$@
 endif
 
 .DEFAULT_GOAL := all
@@ -149,7 +149,7 @@ cabal clean, this script will need to download dependencies.
 
 * [ ] Can it do that without polluting the generated file with status updates from cabal saying
       that it has downloaded this or that dependency[^silent-script]?
-      
+
 [^silent-script]: The Haskell script must run silently for this to work.
 
 ```
@@ -182,4 +182,4 @@ updo/project-dhall/pkgs-sorted.hs > .updo/pkgs-sorted.dhall
 
 - `ghc-x.y.z.dhall2yaml2stack.yaml`
 - `ghc-x.y.z.stack2cabal.project`
-- `ghc-x.y.z.cabal2stack.yaml`
\ No newline at end of file
+- `ghc-x.y.z.cabal2stack.yaml`
diff --git a/alternatives/yaml2stack/README.md b/alternatives/yaml2stack/README.md
index 74c0fba..1dc6e73 100644
--- a/alternatives/yaml2stack/README.md
+++ b/alternatives/yaml2stack/README.md
@@ -10,4 +10,4 @@ dependencies.
 
 [^working-dir]: The `.yaml` fragments are written to `.updo/dhall2yaml2stack`,
 copied to a bash `$(mktemp -d)` temporary directory and then stitched together
-there. There's a note in the make file explaining how to keep these fragments.
\ No newline at end of file
+there. There's a note in the make file explaining how to keep these fragments.
diff --git a/empty/constraints.dhall b/empty/constraints.dhall
index e277cfb..4b91424 100644
--- a/empty/constraints.dhall
+++ b/empty/constraints.dhall
@@ -1 +1 @@
-[] : List { dep : Text, ver : Text }
\ No newline at end of file
+[] : List { dep : Text, ver : Text }
diff --git a/empty/source-pkgs.dhall b/empty/source-pkgs.dhall
index 65a2658..b79faa8 100644
--- a/empty/source-pkgs.dhall
+++ b/empty/source-pkgs.dhall
@@ -1 +1 @@
-[] : List { loc : Text, tag : Text, sub : List Text }
\ No newline at end of file
+[] : List { loc : Text, tag : Text, sub : List Text }
diff --git a/fix-whitespace.yaml b/fix-whitespace.yaml
new file mode 100644
index 0000000..5b8abd0
--- /dev/null
+++ b/fix-whitespace.yaml
@@ -0,0 +1,15 @@
+excluded-dirs:
+  - "dist-newstyle"
+
+excluded-files:
+  - "**/*.mk"
+  - "**/Makefile"
+
+included-files:
+  - "**/*.cabal"
+  - "**/*.dhall"
+  - "**/*.hs"
+  - "**/*.md"
+  - "**/*.project"
+  - "**/*.yaml"
+  - "**/*.yml"
diff --git a/fourmolu.yaml b/fourmolu.yaml
index 641857e..aeb2f5a 100644
--- a/fourmolu.yaml
+++ b/fourmolu.yaml
@@ -11,4 +11,4 @@ let-style: auto
 in-style: left-align
 respectful: true
 fixities: []
-unicode: never
\ No newline at end of file
+unicode: never
diff --git a/project-dhall2config/README.md b/project-dhall2config/README.md
index 79ae8a4..0d153f8 100644
--- a/project-dhall2config/README.md
+++ b/project-dhall2config/README.md
@@ -24,4 +24,4 @@ build-info: True
 For this rule using `make --jobs`[^parallel-make] will speed up the recipe a
 lot.
 
-[^parallel-make]: https://www.gnu.org/software/make/manual/html_node/Parallel.html
\ No newline at end of file
+[^parallel-make]: https://www.gnu.org/software/make/manual/html_node/Parallel.html
diff --git a/project-nix/README.md b/project-nix/README.md
index 8b5fca2..f0fd9f3 100644
--- a/project-nix/README.md
+++ b/project-nix/README.md
@@ -64,4 +64,4 @@ The `Makefile` also has `project-versions.nix` as a target.
 }
 ```
 
-[^sorted]: Renamed from `sha256map-regenerate.py` and modified to sort the map by keys.
\ No newline at end of file
+[^sorted]: Renamed from `sha256map-regenerate.py` and modified to sort the map by keys.
diff --git a/project-skeleton/pkgs/all-in-one.dhall b/project-skeleton/pkgs/all-in-one.dhall
index 09ef423..13aa928 100644
--- a/project-skeleton/pkgs/all-in-one.dhall
+++ b/project-skeleton/pkgs/all-in-one.dhall
@@ -20,7 +20,7 @@
 -- There is no <pkgname>.cabal package file or cabal.project file. To build
 -- packages locally you need at minimum a <pkgname>.cabal file. You can use 'cabal
 -- init' to create one.
--- 
+--
 -- For non-trivial projects you will also want a cabal.project file in the root
 -- directory of your project. This file lists the packages in your project and all
 -- other build configuration. See the Cabal user guide for full details.