diff --git a/src/main/java/sh/libre/scim/event/ScimEventListenerProvider.java b/src/main/java/sh/libre/scim/event/ScimEventListenerProvider.java
index 0180de0621..a36dc57407 100644
--- a/src/main/java/sh/libre/scim/event/ScimEventListenerProvider.java
+++ b/src/main/java/sh/libre/scim/event/ScimEventListenerProvider.java
@@ -27,15 +27,16 @@ public class ScimEventListenerProvider implements EventListenerProvider {
 
     private final KeycloakSession session;
 
-    private final Map<ResourceType, Pattern> patterns = new HashMap<>();
+    private final Map<ResourceType, Pattern> patterns = Map.of(
+            ResourceType.USER, Pattern.compile("users/(.+)"),
+            ResourceType.GROUP, Pattern.compile("groups/([\\w-]+)(/children)?"),
+            ResourceType.GROUP_MEMBERSHIP, Pattern.compile("users/(.+)/groups/(.+)"),
+            ResourceType.REALM_ROLE_MAPPING, Pattern.compile("^(.+)/(.+)/role-mappings")
+    );
 
     public ScimEventListenerProvider(KeycloakSession session) {
         this.session = session;
         dispatcher = new ScimDispatcher(session);
-        patterns.put(ResourceType.USER, Pattern.compile("users/(.+)"));
-        patterns.put(ResourceType.GROUP, Pattern.compile("groups/([\\w-]+)(/children)?"));
-        patterns.put(ResourceType.GROUP_MEMBERSHIP, Pattern.compile("users/(.+)/groups/(.+)"));
-        patterns.put(ResourceType.REALM_ROLE_MAPPING, Pattern.compile("^(.+)/(.+)/role-mappings"));
     }
 
     @Override