diff --git a/maven-resolver-api/src/main/java/org/eclipse/aether/DefaultRepositorySystemSession.java b/maven-resolver-api/src/main/java/org/eclipse/aether/DefaultRepositorySystemSession.java
index 4450487f6..7ed9313a5 100644
--- a/maven-resolver-api/src/main/java/org/eclipse/aether/DefaultRepositorySystemSession.java
+++ b/maven-resolver-api/src/main/java/org/eclipse/aether/DefaultRepositorySystemSession.java
@@ -816,9 +816,9 @@ private void verifyStateForMutation()
         {
             throw new IllegalStateException( "repository system session is read-only" );
         }
-        if ( isClosed() )
+        if ( closed.get() )
         {
-            throw new IllegalStateException( "repository system session is closed" );
+            throw new IllegalStateException( "repository system session is already closed" );
         }
     }
 
@@ -894,8 +894,11 @@ public Collection<FileTransformer> getTransformersForArtifact( Artifact artifact
     @Override
     public void addOnCloseHandler( Consumer<RepositorySystemSession> handler )
     {
-        verifyStateForMutation();
         requireNonNull( handler, "handler cannot be null" );
+        if ( closed.get() )
+        {
+            throw new IllegalStateException( "repository system session is already closed" );
+        }
         onCloseHandlers.add( 0, handler );
     }