diff --git a/aiohttp/client_reqrep.py b/aiohttp/client_reqrep.py
index bea76d84c39..9158c26325a 100644
--- a/aiohttp/client_reqrep.py
+++ b/aiohttp/client_reqrep.py
@@ -209,7 +209,7 @@ def _merge_ssl_params(
     return ssl
 
 
-@attr.s(auto_attribs=True, slots=True, frozen=True)
+@attr.s(auto_attribs=True, slots=True, frozen=True, cache_hash=True)
 class ConnectionKey:
     # the key should contain an information about used proxy / TLS
     # to prevent reusing wrong connections from a pool