diff --git a/src/ZODB/Connection.py b/src/ZODB/Connection.py
index d1722b866..45b53b996 100644
--- a/src/ZODB/Connection.py
+++ b/src/ZODB/Connection.py
@@ -283,8 +283,7 @@ def close(self, primary=True):
             raise ConnectionStateError("Cannot close a connection joined to "
                                        "a transaction")
 
-        if self._cache is not None:
-            self._cache.incrgc() # This is a good time to do some GC
+        self._cache.incrgc() # This is a good time to do some GC
 
         # Call the close callbacks.
         if self.__onCloseCallbacks is not None:
@@ -924,8 +923,7 @@ def open(self, transaction_manager=None, delegate=True):
 
         transaction_manager.registerSynch(self)
 
-        if self._cache is not None:
-            self._cache.incrgc() # This is a good time to do some GC
+        self._cache.incrgc() # This is a good time to do some GC
 
         if delegate:
             # delegate open to secondary connections
@@ -951,7 +949,7 @@ def _release_resources(self):
                 c._storage.release()
             c._storage = c._normal_storage = None
             c._cache = PickleCache(self, 0, 0)
-            c.transaction_manager = None
+            c.close(False)
 
     ##########################################################################
     # Python protocol
diff --git a/src/ZODB/DB.py b/src/ZODB/DB.py
index 5a47d26cf..5da9fb543 100644
--- a/src/ZODB/DB.py
+++ b/src/ZODB/DB.py
@@ -24,7 +24,7 @@
 
 from ZODB.broken import find_global
 from ZODB.utils import z64
-from ZODB.Connection import Connection, TransactionMetaData
+from ZODB.Connection import Connection, TransactionMetaData, noop
 from ZODB._compat import Pickler, _protocol, BytesIO
 import ZODB.serialize
 
@@ -646,15 +646,15 @@ def close(self):
         is closed, so they stop behaving usefully.  Perhaps close()
         should also close all the Connections.
         """
-        noop = lambda *a: None
         self.close = noop
 
         @self._connectionMap
-        def _(c):
-            if c.transaction_manager is not None:
-                c.transaction_manager.abort()
-            c.afterCompletion = c.newTransaction = c.close = noop
-            c._release_resources()
+        def _(conn):
+            if conn.transaction_manager is not None:
+                for c in six.itervalues(conn.connections):
+                    c.explicit_transactions = True
+                conn.transaction_manager.abort()
+            conn._release_resources()
 
         self._mvcc_storage.close()
         del self.storage