diff --git a/.0pdd.yml b/.0pdd.yml
index 36d0a7feee..91dab09e4e 100644
--- a/.0pdd.yml
+++ b/.0pdd.yml
@@ -1,3 +1,4 @@
+---
 errors:
   - yegor256@gmail.com
 # alerts:
diff --git a/.codacy.yml b/.codacy.yml
index 9d54c54c28..e2c8592ccf 100644
--- a/.codacy.yml
+++ b/.codacy.yml
@@ -1,6 +1,7 @@
 # @todo #1326:30min Enable only necessary tests. Several checks
 #  are not available for the project. For example a lot of
 #  package name contains capital letter and such names are conventional.
+---
 exclude_paths:
   - "eo-runtime/src/main/java/EOorg/EOeolang/EOcage$EOencaged$EOencage.java"
   - "eo-runtime/src/main/java/EOorg/EOeolang/Cages.java"
diff --git a/.markdownlint.yml b/.markdownlint.yml
index 7bf567f1ae..f2a8a2bcd9 100644
--- a/.markdownlint.yml
+++ b/.markdownlint.yml
@@ -1,3 +1,4 @@
+---
 # Default state for all rules
 default: true
 
@@ -7,7 +8,7 @@ MD013:
 
 # Inline HTML : https://github.com/DavidAnson/markdownlint/blob/v0.33.0/doc/md033.md
 MD033:
-  allowed_elements: [img]
+  allowed_elements: [ img ]
 
 # Fenced code blocks should have a language specified : https://github.com/DavidAnson/markdownlint/blob/v0.33.0/doc/md040.md
 MD040: false
diff --git a/.rultor.yml b/.rultor.yml
index 225aa2db49..4ab42ed64f 100644
--- a/.rultor.yml
+++ b/.rultor.yml
@@ -1,3 +1,4 @@
+---
 architect:
   - yegor256
 ec2: