diff --git a/slack_sdk/socket_mode/aiohttp/__init__.py b/slack_sdk/socket_mode/aiohttp/__init__.py
index 7fde17752..936e7c9a5 100644
--- a/slack_sdk/socket_mode/aiohttp/__init__.py
+++ b/slack_sdk/socket_mode/aiohttp/__init__.py
@@ -379,7 +379,7 @@ async def connect(self):
                     autoping=False,
                     heartbeat=self.ping_interval,
                     proxy=self.proxy,
-                    ssl=self.web_client.ssl,
+                    ssl=self.web_client.ssl if self.web_client.ssl is not None else True,
                 )
                 session_id: str = await self.session_id()
                 self.auto_reconnect_enabled = self.default_auto_reconnect_enabled