diff --git a/playwright/_impl/_fetch.py b/playwright/_impl/_fetch.py
index e8b812b92..ac82eab38 100644
--- a/playwright/_impl/_fetch.py
+++ b/playwright/_impl/_fetch.py
@@ -394,7 +394,7 @@ async def _inner_fetch(
                     post_data_buffer = data.encode()
             elif isinstance(data, bytes):
                 post_data_buffer = data
-            elif isinstance(data, (dict, list, int, bool)):
+            elif isinstance(data, (dict, list, int, float, bool)):
                 try:
                     # NaN and Infinity are not valid JSON.
                     json_data = json.dumps(data, allow_nan=False)
diff --git a/tests/async/test_fetch_global.py b/tests/async/test_fetch_global.py
index e09567f71..eabd84942 100644
--- a/tests/async/test_fetch_global.py
+++ b/tests/async/test_fetch_global.py
@@ -467,6 +467,7 @@ async def test_should_serialize_request_data(
         ([], "[]"),
         ({}, "{}"),
         ("", ""),
+        (1.5, "1.5"),
     ]:
         response = await request.post(server.PREFIX + "/echo", data=data)
         assert response.status == 200