diff --git a/lib/sqlalchemy/orm/persistence.py b/lib/sqlalchemy/orm/persistence.py
index c4a9402fbc..81024c41f1 100644
--- a/lib/sqlalchemy/orm/persistence.py
+++ b/lib/sqlalchemy/orm/persistence.py
@@ -494,12 +494,12 @@ def _collect_update_commands(
                         params[col.key] = history.added[0]
                 else:
                     pk_params[col._label] = history.unchanged[0]
+                if pk_params[col._label] is None:
+                    raise orm_exc.FlushError(
+                        "Can't update table %s using NULL for primary "
+                        "key value on column %s" % (table, col))
 
         if params or value_params:
-            if None in pk_params.values():
-                raise orm_exc.FlushError(
-                    "Can't update table using NULL for primary "
-                    "key value")
             params.update(pk_params)
             yield (
                 state, state_dict, params, mapper,
diff --git a/test/orm/test_unitofwork.py b/test/orm/test_unitofwork.py
index 247c5e7a80..ae5a8ef60f 100644
--- a/test/orm/test_unitofwork.py
+++ b/test/orm/test_unitofwork.py
@@ -2479,7 +2479,8 @@ class PartialNullPKTest(fixtures.MappedTest):
         t1.col2 = 5
         assert_raises_message(
             orm_exc.FlushError,
-            "Can't update table using NULL for primary key value",
+            "Can't update table t1 using NULL for primary "
+            "key value on column t1.col2",
             s.commit
         )
 
@@ -2492,7 +2493,8 @@ class PartialNullPKTest(fixtures.MappedTest):
         t1.col3 = 'hi'
         assert_raises_message(
             orm_exc.FlushError,
-            "Can't update table using NULL for primary key value",
+            "Can't update table t1 using NULL for primary "
+            "key value on column t1.col2",
             s.commit
         )