diff --git a/aiida/storage/psql_dos/orm/__init__.py b/aiida/storage/psql_dos/orm/__init__.py
index 3d85826a21..2a961436af 100644
--- a/aiida/storage/psql_dos/orm/__init__.py
+++ b/aiida/storage/psql_dos/orm/__init__.py
@@ -8,3 +8,26 @@
 # For further information please visit http://www.aiida.net               #
 ###########################################################################
 """Implementation of ORM backend entities."""
+import warnings
+
+from sqlalchemy.exc import SAWarning
+
+# The :meth:`sqlalchemy.orm.unitofwork.UOWTransaction.register_object` method emits a warning whenever an object is
+# registered that is not part of the session. This can happen when the session is committed or flushed and an object
+# inside the session contains a reference to another object, for example through a relationship, is not explicitly part
+# of the session. If that referenced object is not already stored and persisted, it might get lost. On the other hand,
+# if the object was already persisted before, there is no risk.
+#
+# This situation occurs a lot in AiiDA's code base. Prime example is when a new process is created. Typically the input
+# nodes are either already stored, or stored first. As soon as they get stored, the session is committed and the session
+# is reset by expiring all objects. Now, the input links are created from the input nodes to the process node, and at
+# the end the process node is stored to commit and persist it with the links. It is at this point that Sqlalchemy
+# realises that the input nodes are not explicitly part of the session.
+#
+# One direct solution would be to add the input nodes again to the session before committing the process node and the
+# links. However, this code is part of the backend independent :mod:`aiida.orm` module and this is a backend-specific
+# problem. This is also just one example and there are most likely other places in the code where the problem arises.
+# Therefore, as a work around, the specific warning is ignored through a warrning filter.
+warnings.filterwarnings(
+    'ignore', category=SAWarning, message='Object of type .* not in session, .* operation along .* will not proceed'
+)
diff --git a/docs/source/nitpick-exceptions b/docs/source/nitpick-exceptions
index 0f3aed4811..8be012bbf5 100644
--- a/docs/source/nitpick-exceptions
+++ b/docs/source/nitpick-exceptions
@@ -205,6 +205,7 @@ py:class sqlalchemy.orm.decl_api.SqliteModel
 py:class sqlalchemy.orm.decl_api.Base
 py:class sqlalchemy.sql.compiler.TypeCompiler
 py:class sqlalchemy.sql.elements.BooleanClauseList
+py:meth sqlalchemy.orm.unitofwork.UOWTransaction.register_object
 
 py:class sphinx.ext.autodoc.ClassDocumenter
 py:class sphinx.util.docutils.SphinxDirective
diff --git a/pyproject.toml b/pyproject.toml
index 7a47d39d63..7e1d43cec3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -344,6 +344,7 @@ filterwarnings = [
     "ignore::DeprecationWarning:pymatgen:",
     "ignore::DeprecationWarning:jsonbackend:",
     "ignore::DeprecationWarning:pkg_resources:",
+    "ignore:Object of type .* not in session, .* operation along .* will not proceed:sqlalchemy.exc.SAWarning",
     "ignore::pytest.PytestCollectionWarning",
     "default::ResourceWarning",
 ]