diff --git a/config/extension.neon b/config/extension.neon
index 312e210..a5604d8 100644
--- a/config/extension.neon
+++ b/config/extension.neon
@@ -194,8 +194,4 @@ services:
     -
         factory: Orrison\MeliorStan\Rules\NumberOfChildren\Config
         arguments:
-            - %meliorstan.number_of_children.maximum%
-    -
-        class: Orrison\MeliorStan\Rules\NumberOfChildren\NumberOfChildrenCollector
-        tags:
-            - phpstan.collector
\ No newline at end of file
+            - %meliorstan.number_of_children.maximum%
\ No newline at end of file
diff --git a/docs/NumberOfChildren.md b/docs/NumberOfChildren.md
index bdc1bc8..c257520 100644
--- a/docs/NumberOfChildren.md
+++ b/docs/NumberOfChildren.md
@@ -15,7 +15,7 @@ This rule supports the following configuration option:
 
 ## Usage
 
-Add the rule to your PHPStan configuration:
+This rule relies on a PHPStan collector to gather inheritance information, so you must register both the rule and the collector when enabling it. Add the following to your PHPStan configuration:
 
 ```neon
 includes:
@@ -24,6 +24,12 @@ includes:
 rules:
     - Orrison\MeliorStan\Rules\NumberOfChildren\NumberOfChildrenRule
 
+services:
+    -
+        class: Orrison\MeliorStan\Rules\NumberOfChildren\NumberOfChildrenCollector
+        tags:
+            - phpstan.collector
+
 parameters:
     meliorstan:
         number_of_children:
@@ -93,5 +99,6 @@ class Child6 extends PopularParent {} // ✗ This 6th child causes the violation
 
 - **Direct children only**: This rule counts only direct subclasses (classes that directly extend the parent), not grandchildren or deeper descendants.
 - **Cross-file analysis**: The rule uses PHPStan collectors to analyze class hierarchies across all files in your project.
+- **Collector registration required**: Remember to register `NumberOfChildrenCollector` in any PHPStan config where you enable this rule.
 - **Per-class violation**: The violation is reported on the parent class, not on its children.
 - **Design consideration**: A high number of direct children often suggests that the parent class may be too generic or that the hierarchy could benefit from intermediate abstract classes or interfaces.
diff --git a/tests/Rules/NumberOfChildren/config/default.neon b/tests/Rules/NumberOfChildren/config/default.neon
index 3963490..6d1a30a 100644
--- a/tests/Rules/NumberOfChildren/config/default.neon
+++ b/tests/Rules/NumberOfChildren/config/default.neon
@@ -4,6 +4,12 @@ includes:
 rules:
     - Orrison\MeliorStan\Rules\NumberOfChildren\NumberOfChildrenRule
 
+services:
+    -
+        class: Orrison\MeliorStan\Rules\NumberOfChildren\NumberOfChildrenCollector
+        tags:
+            - phpstan.collector
+
 parameters:
     meliorstan:
         number_of_children:
diff --git a/tests/Rules/NumberOfChildren/config/maximum-one.neon b/tests/Rules/NumberOfChildren/config/maximum-one.neon
index 844692f..8058394 100644
--- a/tests/Rules/NumberOfChildren/config/maximum-one.neon
+++ b/tests/Rules/NumberOfChildren/config/maximum-one.neon
@@ -4,6 +4,12 @@ includes:
 rules:
     - Orrison\MeliorStan\Rules\NumberOfChildren\NumberOfChildrenRule
 
+services:
+    -
+        class: Orrison\MeliorStan\Rules\NumberOfChildren\NumberOfChildrenCollector
+        tags:
+            - phpstan.collector
+
 parameters:
     meliorstan:
         number_of_children:
diff --git a/tests/Rules/NumberOfChildren/config/maximum-two.neon b/tests/Rules/NumberOfChildren/config/maximum-two.neon
index fbd0ace..b4be48e 100644
--- a/tests/Rules/NumberOfChildren/config/maximum-two.neon
+++ b/tests/Rules/NumberOfChildren/config/maximum-two.neon
@@ -4,6 +4,12 @@ includes:
 rules:
     - Orrison\MeliorStan\Rules\NumberOfChildren\NumberOfChildrenRule
 
+services:
+    -
+        class: Orrison\MeliorStan\Rules\NumberOfChildren\NumberOfChildrenCollector
+        tags:
+            - phpstan.collector
+
 parameters:
     meliorstan:
         number_of_children: