diff --git a/h/db/__init__.py b/h/db/__init__.py
index a0cabd3b775..276408d60c9 100644
--- a/h/db/__init__.py
+++ b/h/db/__init__.py
@@ -115,6 +115,21 @@ def close_the_sqlalchemy_session(request):
             })
         session.close()
 
+        # zope.sqlalchemy maintains an internal `id(session) => state` map for
+        # each active DB session which is registered with it.
+        #
+        # Ensure that this is empty at the end of the request as otherwise it
+        # can cause request <=> DB transaction integration to break in future
+        # requests if a future `Session` object reuses the same ID.
+        dm = zope.sqlalchemy.datamanager
+        if len(dm._SESSION_STATE) > 0:
+            log.warn('request ended with non-empty zope.sqlalchemy state', extra={
+                'data': {
+                    'zope.sqlalchemy.datamanager._SESSION_STATE': dm._SESSION_STATE,
+                },
+            })
+            dm._SESSION_STATE = {}
+
     return session