diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 0a6be58e..73568418 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -17,9 +17,9 @@ build_docs:
     paths:
       - _build
   script:
-      - apt-get -y install python3-pip python3-sphinx
-      - pip3 install recommonmark
-      - ./doc/build.sh _build
+    - apt-get -y install python3-pip python3-sphinx
+    - pip3 install recommonmark
+    - ./doc/build.sh _build
   except:
     variables:
       - $PKG_ONLY == "1"
@@ -42,33 +42,37 @@ build_deb:
   stage: build
   artifacts:
     paths:
-      - "*.deb"
+      - '*.deb'
   script:
-      - rm -f ../*.deb
-      - apt-get -y build-dep .
-      - apt-get -y install devscripts
-      - REV=$(git log -1 --format=%h)
-      - VER=$(dpkg-parsechangelog -SVersion)
-      - 'DEBFULLNAME="Librem5 CI" EMAIL="librem5-builds@lists.community.puri.sm" dch -v"$VER+librem5ci$CI_PIPELINE_ID.$REV" "$MSG"'
-      - debuild -i -us -uc -b
-      - cp ../*.deb .
+    - rm -f ../*.deb
+    - apt-get -y build-dep .
+    - apt-get -y install devscripts
+    - REV=$(git log -1 --format=%h)
+    - VER=$(dpkg-parsechangelog -SVersion)
+    - DEBFULLNAME="Librem5 CI"
+    - EMAIL="librem5-builds@lists.community.puri.sm"
+    - dch -v"$VER+librem5ci$CI_PIPELINE_ID.$REV" "$MSG"
+    - debuild -i -us -uc -b
+    - cp ../*.deb .
 
 build_deb:arm64:
   tags:
-      - aarch64
+    - aarch64
   stage: build
   artifacts:
     paths:
-      - "*.deb"
+      - '*.deb'
   script:
-      - rm -f ../*.deb
-      - apt-get -y build-dep .
-      - apt-get -y install devscripts
-      - REV=$(git log -1 --format=%h)
-      - VER=$(dpkg-parsechangelog -SVersion)
-      - 'DEBFULLNAME="Librem5 CI" EMAIL="librem5-builds@lists.community.puri.sm" dch -v"$VER+librem5ci$CI_PIPELINE_ID.$REV" "$MSG"'
-      - debuild -i -us -uc -b
-      - cp ../*.deb .
+    - rm -f ../*.deb
+    - apt-get -y build-dep .
+    - apt-get -y install devscripts
+    - REV=$(git log -1 --format=%h)
+    - VER=$(dpkg-parsechangelog -SVersion)
+    - DEBFULLNAME="Librem5 CI"
+    - EMAIL="librem5-builds@lists.community.puri.sm"
+    - dch -v"$VER+librem5ci$CI_PIPELINE_ID.$REV" "$MSG"
+    - debuild -i -us -uc -b
+    - cp ../*.deb .
 
 test_lintian:
   stage: test
diff --git a/tools/yamlfmt b/tools/yamlfmt
new file mode 100755
index 00000000..0aef3523
--- /dev/null
+++ b/tools/yamlfmt
@@ -0,0 +1,36 @@
+#!/usr/bin/env python3
+
+"""Checks YAML files for correct formatting.
+Usage: yamlfmt.py [--apply] file.yaml
+"""
+
+import ruamel.yaml
+import sys
+
+args = sys.argv[:]
+try:
+    args.remove('--apply')
+    want_apply = True
+except ValueError:
+    want_apply = False
+
+path = args[1]
+
+with open(path) as f:
+    contents = f.read()
+    yml = ruamel.yaml.round_trip_load(contents)
+    formatted = ruamel.yaml.round_trip_dump(yml, block_seq_indent=2)
+    well_formatted = formatted == contents
+        
+if not well_formatted:
+    print('The yaml file is not correctly formatted:', path)
+    if want_apply:
+        print('Correcting', path)
+        with open(path, 'w') as f:
+            f.write(formatted)
+    else:
+        print('Please use the following correction:')
+        print('----------corrected', path)
+        print(formatted)
+        print('----------end corrected', path)
+        sys.exit(1)