diff --git a/datasette/views/table.py b/datasette/views/table.py
index 5643858d..7027bb10 100644
--- a/datasette/views/table.py
+++ b/datasette/views/table.py
@@ -461,6 +461,13 @@ class TableInsertView(BaseView):
                             i, '", "'.join(missing_pks)
                         )
                     )
+                null_pks = [pk for pk in pks_list if pk in row and row[pk] is None]
+                if null_pks:
+                    errors.append(
+                        'Row {} has null primary key column(s): "{}"'.format(
+                            i, '", "'.join(null_pks)
+                        )
+                    )
             invalid_columns = set(row.keys()) - columns
             if invalid_columns and not extras.get("alter"):
                 errors.append(
diff --git a/tests/test_api_write.py b/tests/test_api_write.py
index adf8d310..91a88606 100644
--- a/tests/test_api_write.py
+++ b/tests/test_api_write.py
@@ -299,6 +299,14 @@ async def test_insert_rows(ds_write, return_rows):
             400,
             ['Row 0 is missing primary key column(s): "id"'],
         ),
+        # null primary key
+        (
+            "/data/docs/-/upsert",
+            {"rows": [{"id": None, "title": "Null PK"}]},
+            None,
+            400,
+            ['Row 0 has null primary key column(s): "id"'],
+        ),
         # Upsert does not support ignore or replace
         (
             "/data/docs/-/upsert",