diff --git a/datasette/views/base.py b/datasette/views/base.py
index 219630af00..348f0c031e 100644
--- a/datasette/views/base.py
+++ b/datasette/views/base.py
@@ -362,6 +362,8 @@ async def get_format(self, request, database, args):
         _format = request.args.get("_format", None)
         if not _format:
             _format = (args.pop("as_format", None) or "").lstrip(".")
+        else:
+            args.pop("as_format", None)
         if "table_and_format" in args:
             db = self.ds.databases[database]
 
diff --git a/tests/test_api.py b/tests/test_api.py
index 826c00f31b..a734b8de62 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -1107,6 +1107,15 @@ def test_row(app_client):
     assert [{"id": "1", "content": "hello"}] == response.json["rows"]
 
 
+def test_row_format_in_querystring(app_client):
+    # regression test for https://github.com/simonw/datasette/issues/563
+    response = app_client.get(
+        "/fixtures/simple_primary_key/1?_format=json&_shape=objects"
+    )
+    assert response.status == 200
+    assert [{"id": "1", "content": "hello"}] == response.json["rows"]
+
+
 def test_row_strange_table_name(app_client):
     response = app_client.get(
         "/fixtures/table%2Fwith%2Fslashes.csv/3.json?_shape=objects"