diff --git a/CHANGES/2523.bugfix b/CHANGES/2523.bugfix
new file mode 100644
index 00000000000..879ec21b378
--- /dev/null
+++ b/CHANGES/2523.bugfix
@@ -0,0 +1 @@
+Fix warning in `ClientSession.__del__` by stopping to try to close it.
diff --git a/aiohttp/client.py b/aiohttp/client.py
index 8bbf0d4c7ef..6a0370fe846 100644
--- a/aiohttp/client.py
+++ b/aiohttp/client.py
@@ -126,8 +126,6 @@ def __init__(self, *, connector=None, loop=None, cookies=None,
 
     def __del__(self, _warnings=warnings):
         if not self.closed:
-            self.close()
-
             _warnings.warn("Unclosed client session {!r}".format(self),
                            ResourceWarning)
             context = {'client_session': self,