diff --git a/datasette/renderer.py b/datasette/renderer.py
index 349c29223c..3f921fe77d 100644
--- a/datasette/renderer.py
+++ b/datasette/renderer.py
@@ -32,7 +32,7 @@ def json_renderer(args, data, view_name):
     # Handle the _json= parameter which may modify data["rows"]
     json_cols = []
     if "_json" in args:
-        json_cols = args["_json"]
+        json_cols = args.getlist("_json")
     if json_cols and "rows" in data and "columns" in data:
         data["rows"] = convert_specific_columns_to_json(
             data["rows"], data["columns"], json_cols
diff --git a/datasette/utils/__init__.py b/datasette/utils/__init__.py
index 9b4f21ba28..bf96541399 100644
--- a/datasette/utils/__init__.py
+++ b/datasette/utils/__init__.py
@@ -753,17 +753,41 @@ def escape_fts(query):
     )
 
 
-class RequestParameters(dict):
+class RequestParameters:
+    def __init__(self, data):
+        # data is a dictionary of key => [list, of, values]
+        assert isinstance(data, dict), "data should be a dictionary of key => [list]"
+        for key in data:
+            assert isinstance(
+                data[key], list
+            ), "data should be a dictionary of key => [list]"
+        self._data = data
+
+    def __contains__(self, key):
+        return key in self._data
+
+    def __getitem__(self, key):
+        return self._data[key][0]
+
+    def keys(self):
+        return self._data.keys()
+
+    def __iter__(self):
+        yield from self._data.keys()
+
+    def __len__(self):
+        return len(self._data)
+
     def get(self, name, default=None):
         "Return first value in the list, if available"
         try:
-            return super().get(name)[0]
+            return self._data.get(name)[0]
         except (KeyError, TypeError):
             return default
 
     def getlist(self, name):
         "Return full list"
-        return super().get(name) or []
+        return self._data.get(name) or []
 
 
 class ConnectionProblem(Exception):
diff --git a/datasette/utils/asgi.py b/datasette/utils/asgi.py
index 62a2a0c83b..24398b7724 100644
--- a/datasette/utils/asgi.py
+++ b/datasette/utils/asgi.py
@@ -63,11 +63,6 @@ def query_string(self):
     def args(self):
         return RequestParameters(parse_qs(qs=self.query_string))
 
-    @property
-    def raw_args(self):
-        # Deprecated, undocumented - may be removed in Datasette 1.0
-        return {key: value[0] for key, value in self.args.items()}
-
     async def post_vars(self):
         body = []
         body = b""
diff --git a/datasette/views/table.py b/datasette/views/table.py
index d1d92bb1d9..a629346fdf 100644
--- a/datasette/views/table.py
+++ b/datasette/views/table.py
@@ -277,11 +277,11 @@ async def data(
         # it can still be queried using ?_col__exact=blah
         special_args = {}
         other_args = []
-        for key, value in args.items():
+        for key in args:
             if key.startswith("_") and "__" not in key:
-                special_args[key] = value[0]
+                special_args[key] = args[key]
             else:
-                for v in value:
+                for v in args.getlist(key):
                     other_args.append((key, v))
 
         # Handle ?_filter_column and redirect, if present
diff --git a/docs/internals.rst b/docs/internals.rst
index bbf10caedf..ea015dbc27 100644
--- a/docs/internals.rst
+++ b/docs/internals.rst
@@ -268,12 +268,16 @@ The object also has one awaitable method:
 The RequestParameters class
 ---------------------------
 
-This class, returned by ``request.args``, is a subclass of a Python dictionary that provides methods for working with keys that map to lists of values.
+This class, returned by ``request.args``, is a dictionary-like object.
 
-Conider the querystring ``?foo=1&foo=2``. This will produce a ``request.args`` that looks like this::
+Consider the querystring ``?foo=1&foo=2``. This will produce a ``request.args`` that looks like this::
 
     RequestParameters({"foo": ["1", "2"]})
 
-Calling ``request.args.get("foo")`` will return the first value, ``"1"``. If that key is not present it will return ``None`` - or the second argument if you passed one, which will be used as the default.
+``request.args["foo"]`` returns the first value, ``"1"`` - or raises ``KeyError`` if that key is missing.
 
-Calling ``request.args.getlist("foo")`` will return the full list, ``["1", "2"]``. If you call it on a missing key it will return ``[]``.
+``request.args.get("foo")`` returns ``"1"`` - or ``None`` if the key is missing. A second argument can be used to specify a different default value.
+
+``request.args.getlist("foo")`` returns the full list, ``["1", "2"]``. If you call it on a missing key it will return ``[]``.
+
+You can use ``if key in request.args`` to check if a key is present. ``for key in request.args`` will iterate through the keys, or you can use ``request.args.keys()`` to get all of the keys.
diff --git a/tests/test_utils.py b/tests/test_utils.py
index ffb66ca58a..9d6f45b0cb 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -452,8 +452,18 @@ def test_request_args():
     request = Request.fake("/foo?multi=1&multi=2&single=3")
     assert "1" == request.args.get("multi")
     assert "3" == request.args.get("single")
+    assert "1" == request.args["multi"]
+    assert "3" == request.args["single"]
     assert ["1", "2"] == request.args.getlist("multi")
     assert [] == request.args.getlist("missing")
+    assert "multi" in request.args
+    assert "single" in request.args
+    assert "missing" not in request.args
+    expected = ["multi", "single"]
+    assert expected == list(request.args.keys())
+    for i, key in enumerate(request.args):
+        assert expected[i] == key
+    assert 2 == len(request.args)
     with pytest.raises(KeyError):
         request.args["missing"]