diff --git a/lib/net/http/persistent/pool.rb b/lib/net/http/persistent/pool.rb
index 90fd92b..8990006 100644
--- a/lib/net/http/persistent/pool.rb
+++ b/lib/net/http/persistent/pool.rb
@@ -20,6 +20,9 @@ def checkin net_http_args
 
     if stack.empty?
       @available.push conn, connection_args: net_http_args
+
+      Thread.current[@key].delete(net_http_args)
+      Thread.current[@key] = nil if Thread.current[@key].empty?
     end
 
     nil