diff --git a/src/main/java/org/commonjava/util/jhttpc/INTERNAL/conn/ConnectionManagerCache.java b/src/main/java/org/commonjava/util/jhttpc/INTERNAL/conn/ConnectionManagerCache.java
index 46c0a4b..5cd353e 100644
--- a/src/main/java/org/commonjava/util/jhttpc/INTERNAL/conn/ConnectionManagerCache.java
+++ b/src/main/java/org/commonjava/util/jhttpc/INTERNAL/conn/ConnectionManagerCache.java
@@ -1,4 +1,4 @@
-/**
+/*
  * Copyright (C) 2015-2024 Red Hat, Inc. (https://github.com/Commonjava/jhttpc)
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
@@ -45,12 +45,14 @@ public class ConnectionManagerCache
     private static final long EXPIRATION_MILLIS = TimeUnit.MILLISECONDS.convert( EXPIRATION_SECONDS, TimeUnit.SECONDS );
 
     private final Map<SiteConnectionConfig, ConnectionManagerTracker> cache =
-            new HashMap<SiteConnectionConfig, ConnectionManagerTracker>();
+            new HashMap<>();
 
     private final Timer timer = new Timer( "jhttpc-connection-manager-cache", true );
 
     private final Logger logger = LoggerFactory.getLogger( getClass() );
 
+    private boolean shutdown;
+
     public ConnectionManagerCache()
     {
         timer.scheduleAtFixedRate( new ExpirationSweeper( this ), EXPIRATION_MILLIS, EXPIRATION_MILLIS );
@@ -60,7 +62,7 @@ public synchronized void expireTrackersOlderThan( long duration, TimeUnit unit )
     {
         long expiration = System.currentTimeMillis() - TimeUnit.MILLISECONDS.convert( duration, unit );
 
-        for ( SiteConnectionConfig config : new HashSet<SiteConnectionConfig>( cache.keySet() ) )
+        for ( SiteConnectionConfig config : new HashSet<>( cache.keySet() ) )
         {
             ConnectionManagerTracker tracker = cache.get( config );
             if ( tracker != null && tracker.getLastRetrieval() < expiration )
@@ -80,13 +82,12 @@ public synchronized void expireTrackersOlderThan( long duration, TimeUnit unit )
     public synchronized ConnectionManagerTracker getTrackerFor( SiteConnectionConfig config )
             throws JHttpCException
     {
-        ConnectionManagerTracker tracker = cache.get( config );
-        if ( tracker == null )
+        if ( shutdown )
         {
-            tracker = new ConnectionManagerTracker( config, this );
-            cache.put( config, tracker );
+            throw new JHttpCException( "Connection manager cache already shut down for: %s", null, config );
         }
 
+        ConnectionManagerTracker tracker = cache.computeIfAbsent( config, c -> new ConnectionManagerTracker( c, this ) );
         return tracker.retrieved();
     }
 
@@ -147,6 +148,8 @@ private synchronized boolean doShutdown( Function<ConnectionManagerTracker, Bool
         }
 
         timer.cancel();
+        shutdown = true;
+        cache.clear();
 
         return result;
     }
@@ -186,7 +189,7 @@ static final class ExpirationSweeper
             extends TimerTask
     {
 
-        private ConnectionManagerCache cache;
+        private final ConnectionManagerCache cache;
 
         public ExpirationSweeper( ConnectionManagerCache cache )
         {
diff --git a/src/main/java/org/commonjava/util/jhttpc/INTERNAL/conn/ConnectionManagerTracker.java b/src/main/java/org/commonjava/util/jhttpc/INTERNAL/conn/ConnectionManagerTracker.java
index f8b0939..4505f9c 100644
--- a/src/main/java/org/commonjava/util/jhttpc/INTERNAL/conn/ConnectionManagerTracker.java
+++ b/src/main/java/org/commonjava/util/jhttpc/INTERNAL/conn/ConnectionManagerTracker.java
@@ -104,7 +104,7 @@ private boolean tryShutdown()
     {
         if ( detached && !isActive() )
         {
-            manager.reallyShutdown();
+            closeManager();
             managerCache.remove( config );
             return true;
         }
@@ -112,6 +112,15 @@ private boolean tryShutdown()
         return false;
     }
 
+    private void closeManager()
+    {
+        if ( manager != null )
+        {
+            manager.reallyShutdown();
+            manager = null;
+        }
+    }
+
     public long getLastRetrieval()
     {
         return lastRetrieval;
@@ -180,7 +189,7 @@ public boolean isShutdown()
     @Override
     public synchronized boolean shutdownNow()
     {
-        manager.reallyShutdown();
+        closeManager();
         return true;
     }
 
@@ -196,7 +205,7 @@ public synchronized boolean shutdownGracefully( final long timeoutMillis )
 
         if ( !isActive() )
         {
-            manager.reallyShutdown();
+            closeManager();
             return true;
         }