diff --git a/cheroot/server.py b/cheroot/server.py
index 11d4930e4b..85036e287b 100644
--- a/cheroot/server.py
+++ b/cheroot/server.py
@@ -1001,6 +1001,9 @@ def read_request_headers(self):
             if self.inheaders.get(b'Connection', b'') != b'Keep-Alive':
                 self.close_connection = True
 
+        if not self.server.connections.can_add_keepalive_connection:
+            self.close_connection = True
+
         # Transfer-Encoding support
         te = None
         if self.response_protocol == 'HTTP/1.1':