diff --git a/.mergify.yml b/.mergify.yml
index 3955cb07..c802ad70 100644
--- a/.mergify.yml
+++ b/.mergify.yml
@@ -7,4 +7,4 @@ rules:
         required_approving_review_count: 1
       required_status_checks:
         contexts:
-        - continuous-integration/travis-ci
+          - continuous-integration/travis-ci
diff --git a/.travis.yml b/.travis.yml
index 79111f22..964cf350 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,9 +10,7 @@ cache:
 
 before_install:
   # `npm ci` is available since npm@5.7.0
-  - if ruby -e "exit(1) if Gem::Version.new(ARGV[0]) >= Gem::Version.new('5.7.0')" $(npm -v); then
-      npm i -g npm@latest;
-    fi
+  - if ruby -e "exit(1) if Gem::Version.new(ARGV[0]) >= Gem::Version.new('5.7.0')" $(npm -v); then npm i -g npm@latest; fi
 
 before_script:
   - commitlint-travis
diff --git a/package.json b/package.json
index 6e8989b3..2570b18c 100644
--- a/package.json
+++ b/package.json
@@ -68,6 +68,10 @@
         "prettier --write",
         "markdownlint",
         "git add"
+      ],
+      "*.{yml,yaml}": [
+        "prettier --write",
+        "git add"
       ]
     },
     "ignore": [
diff --git a/sideci.yml b/sideci.yml
index 88f0bf1d..7d60b4a1 100644
--- a/sideci.yml
+++ b/sideci.yml
@@ -2,5 +2,5 @@ linter:
   eslint:
     npm_install: true
     options:
-      ignore-path: '.gitignore'
-      ext: '.js,.jsx,.mjs'
+      ignore-path: ".gitignore"
+      ext: ".js,.jsx,.mjs"
diff --git a/test/fixtures/package-empty_expected.json b/test/fixtures/package-empty_expected.json
index b4417879..10cde1a0 100644
--- a/test/fixtures/package-empty_expected.json
+++ b/test/fixtures/package-empty_expected.json
@@ -23,6 +23,10 @@
         "prettier --write",
         "markdownlint",
         "git add"
+      ],
+      "*.{yml,yaml}": [
+        "prettier --write",
+        "git add"
       ]
     },
     "ignore": [
diff --git a/test/fixtures/package-normal_expected.json b/test/fixtures/package-normal_expected.json
index c2fdd710..88339af6 100644
--- a/test/fixtures/package-normal_expected.json
+++ b/test/fixtures/package-normal_expected.json
@@ -24,6 +24,10 @@
         "prettier --write",
         "markdownlint",
         "git add"
+      ],
+      "*.{yml,yaml}": [
+        "prettier --write",
+        "git add"
       ]
     },
     "ignore": [