diff --git a/README.rst b/README.rst
index df970911..fd6311eb 100644
--- a/README.rst
+++ b/README.rst
@@ -294,6 +294,7 @@ the recipe:
 * YAML files suffix must be ``.yaml``, not ``.yml``;
 * YAML files must be valid;
 * YAML files must use 4 space indentations;
+* YAML files use ``null`` instead of ``~``;
 * YAML files under config/packages must not define a "parameters" section;
 * JSON files must be valid;
 * JSON files must use 4 space indentations;
diff --git a/nelmio/cors-bundle/1.5/config/packages/nelmio_cors.yaml b/nelmio/cors-bundle/1.5/config/packages/nelmio_cors.yaml
index 6f202c26..c7665081 100644
--- a/nelmio/cors-bundle/1.5/config/packages/nelmio_cors.yaml
+++ b/nelmio/cors-bundle/1.5/config/packages/nelmio_cors.yaml
@@ -7,4 +7,4 @@ nelmio_cors:
         expose_headers: ['Link']
         max_age: 3600
     paths:
-        '^/': ~
+        '^/': null
diff --git a/sensiolabs/security-checker/4.0/config/packages/security_checker.yaml b/sensiolabs/security-checker/4.0/config/packages/security_checker.yaml
index 615e2d76..2e905f7f 100644
--- a/sensiolabs/security-checker/4.0/config/packages/security_checker.yaml
+++ b/sensiolabs/security-checker/4.0/config/packages/security_checker.yaml
@@ -3,6 +3,6 @@ services:
         autowire: true
         autoconfigure: true
 
-    SensioLabs\Security\SecurityChecker: ~
+    SensioLabs\Security\SecurityChecker: null
 
-    SensioLabs\Security\Command\SecurityCheckerCommand: ~
+    SensioLabs\Security\Command\SecurityCheckerCommand: null
diff --git a/symfony/framework-bundle/3.3/config/packages/cache.yaml b/symfony/framework-bundle/3.3/config/packages/cache.yaml
index 93e620ef..4028c9b7 100644
--- a/symfony/framework-bundle/3.3/config/packages/cache.yaml
+++ b/symfony/framework-bundle/3.3/config/packages/cache.yaml
@@ -16,4 +16,4 @@ framework:
 
         # Namespaced pools use the above "app" backend by default
         #pools:
-            #my.dedicated.cache: ~
+            #my.dedicated.cache: null
diff --git a/symfony/framework-bundle/3.3/config/packages/framework.yaml b/symfony/framework-bundle/3.3/config/packages/framework.yaml
index 0eaeae3c..d2b31bff 100644
--- a/symfony/framework-bundle/3.3/config/packages/framework.yaml
+++ b/symfony/framework-bundle/3.3/config/packages/framework.yaml
@@ -6,7 +6,7 @@ framework:
     # Enables session support. Note that the session will ONLY be started if you read or write from it.
     # Remove or comment this section to explicitly disable session support.
     session:
-        handler_id: ~
+        handler_id: null
 
     #esi: true
     #fragments: true
diff --git a/symfony/framework-bundle/4.2/config/packages/framework.yaml b/symfony/framework-bundle/4.2/config/packages/framework.yaml
index 5e25aa4b..6089f4bd 100644
--- a/symfony/framework-bundle/4.2/config/packages/framework.yaml
+++ b/symfony/framework-bundle/4.2/config/packages/framework.yaml
@@ -6,7 +6,7 @@ framework:
     # Enables session support. Note that the session will ONLY be started if you read or write from it.
     # Remove or comment this section to explicitly disable session support.
     session:
-        handler_id: ~
+        handler_id: null
         cookie_secure: auto
         cookie_samesite: lax
 
diff --git a/symfony/routing/3.3/config/packages/routing.yaml b/symfony/routing/3.3/config/packages/routing.yaml
index 368bc7f4..b3e6a0af 100644
--- a/symfony/routing/3.3/config/packages/routing.yaml
+++ b/symfony/routing/3.3/config/packages/routing.yaml
@@ -1,3 +1,3 @@
 framework:
     router:
-        strict_requirements: ~
+        strict_requirements: null
diff --git a/symfony/routing/4.0/config/packages/routing.yaml b/symfony/routing/4.0/config/packages/routing.yaml
index 368bc7f4..b3e6a0af 100644
--- a/symfony/routing/4.0/config/packages/routing.yaml
+++ b/symfony/routing/4.0/config/packages/routing.yaml
@@ -1,3 +1,3 @@
 framework:
     router:
-        strict_requirements: ~
+        strict_requirements: null
diff --git a/symfony/routing/4.2/config/packages/routing.yaml b/symfony/routing/4.2/config/packages/routing.yaml
index a15c4ec6..3d69e1e4 100644
--- a/symfony/routing/4.2/config/packages/routing.yaml
+++ b/symfony/routing/4.2/config/packages/routing.yaml
@@ -1,4 +1,4 @@
 framework:
     router:
-        strict_requirements: ~
+        strict_requirements: null
         utf8: true
diff --git a/symfony/security-bundle/3.3/config/packages/security.yaml b/symfony/security-bundle/3.3/config/packages/security.yaml
index 4c496fb2..855f921e 100644
--- a/symfony/security-bundle/3.3/config/packages/security.yaml
+++ b/symfony/security-bundle/3.3/config/packages/security.yaml
@@ -1,7 +1,7 @@
 security:
     # https://symfony.com/doc/current/security.html#where-do-users-come-from-user-providers
     providers:
-        in_memory: { memory: ~ }
+        in_memory: { memory: null }
     firewalls:
         dev:
             pattern: ^/(_(profiler|wdt)|css|images|js)/
diff --git a/symfony/workflow/3.3/config/packages/workflow.yaml b/symfony/workflow/3.3/config/packages/workflow.yaml
index 2a716ff0..855df59c 100644
--- a/symfony/workflow/3.3/config/packages/workflow.yaml
+++ b/symfony/workflow/3.3/config/packages/workflow.yaml
@@ -1,2 +1,2 @@
 framework:
-    workflows: ~
+    workflows: null
diff --git a/twig/extensions/1.0/config/packages/twig_extensions.yaml b/twig/extensions/1.0/config/packages/twig_extensions.yaml
index 0881cc95..da780f5f 100644
--- a/twig/extensions/1.0/config/packages/twig_extensions.yaml
+++ b/twig/extensions/1.0/config/packages/twig_extensions.yaml
@@ -5,7 +5,7 @@ services:
         autoconfigure: true
 
     # Uncomment any lines below to activate that Twig extension
-    #Twig\Extensions\ArrayExtension: ~
-    #Twig\Extensions\DateExtension: ~
-    #Twig\Extensions\IntlExtension: ~
-    #Twig\Extensions\TextExtension: ~
+    #Twig\Extensions\ArrayExtension: null
+    #Twig\Extensions\DateExtension: null
+    #Twig\Extensions\IntlExtension: null
+    #Twig\Extensions\TextExtension: null