diff --git a/lib/vquic/curl_ngtcp2.c b/lib/vquic/curl_ngtcp2.c
index ff455e52c5..97ef98b971 100644
--- a/lib/vquic/curl_ngtcp2.c
+++ b/lib/vquic/curl_ngtcp2.c
@@ -72,9 +72,9 @@
 #define QUIC_MAX_STREAMS       (256 * 1024)
 #define QUIC_HANDSHAKE_TIMEOUT (10 * NGTCP2_SECONDS)
 
-/* A stream window is the maximum amount we need to buffer for
- * each active transfer.
- * Chunk size is large enough to take a full DATA frame */
+/* We announce a small window size in transport param to the server,
+ * and grow that immediately to max when no rate limit is in place.
+ * We need to start small as we are not able to decrease it. */
 #define H3_STREAM_WINDOW_SIZE_INITIAL (32 * 1024)
 #define H3_STREAM_WINDOW_SIZE_MAX     (10 * 1024 * 1024)
 #define H3_CONN_WINDOW_SIZE_MAX       (100 * H3_STREAM_WINDOW_SIZE_MAX)
@@ -90,10 +90,10 @@
  * spares. Memory consumption goes down when streams run empty,
  * have a large upload done, etc. */
 #define H3_STREAM_POOL_SPARES      2
-/* Receive and Send max number of chunks just follows from the
- * chunk size and window size */
+/* The max amount of un-acked upload data we keep around per stream */
+#define H3_STREAM_SEND_BUFFER_MAX      (10 * 1024 * 1024)
 #define H3_STREAM_SEND_CHUNKS \
-  (H3_STREAM_WINDOW_SIZE_MAX / H3_STREAM_CHUNK_SIZE)
+  (H3_STREAM_SEND_BUFFER_MAX / H3_STREAM_CHUNK_SIZE)
 
 /*
  * Store ngtcp2 version info in this buffer.
diff --git a/tests/http/test_07_upload.py b/tests/http/test_07_upload.py
index 495ec7a989..daead90930 100644
--- a/tests/http/test_07_upload.py
+++ b/tests/http/test_07_upload.py
@@ -639,21 +639,18 @@ class TestUpload:
         ])
         r.check_exit_code(0)
 
-    # nghttpx is the only server we have that supports TLS early data and
-    # has a limit of 16k it announces
+    # nghttpx is the only server we have that supports TLS early data
     @pytest.mark.skipif(condition=not Env.have_nghttpx(), reason="no nghttpx")
-    @pytest.mark.parametrize("proto,upload_size,exp_early", [
-        pytest.param('http/1.1', 100, 203, id='h1-small-body'),
-        pytest.param('http/1.1', 10*1024, 10345, id='h1-medium-body'),
-        pytest.param('http/1.1', 32*1024, 16384, id='h1-limited-body'),
-        pytest.param('h2', 10*1024, 10378, id='h2-medium-body'),
-        pytest.param('h2', 32*1024, 16384, id='h2-limited-body'),
-        pytest.param('h3', 1024, 1126, id='h3-small-body'),
-        pytest.param('h3', 1024 * 1024, 131177, id='h3-limited-body'),
-        # h3: limited+body (long app data). The 0RTT size is limited by
-        # our sendbuf size of 128K.
+    @pytest.mark.parametrize("proto,upload_size", [
+        pytest.param('http/1.1', 100, id='h1-small-body'),
+        pytest.param('http/1.1', 10*1024, id='h1-medium-body'),
+        pytest.param('http/1.1', 32*1024, id='h1-limited-body'),
+        pytest.param('h2', 10*1024, id='h2-medium-body'),
+        pytest.param('h2', 32*1024, id='h2-limited-body'),
+        pytest.param('h3', 1024, id='h3-small-body'),
+        pytest.param('h3', 1024 * 1024, id='h3-limited-body'),
     ])
-    def test_07_70_put_earlydata(self, env: Env, httpd, nghttpx, proto, upload_size, exp_early):
+    def test_07_70_put_earlydata(self, env: Env, httpd, nghttpx, proto, upload_size):
         if not env.curl_can_early_data():
             pytest.skip('TLS earlydata not implemented')
         if proto == 'h2' and not env.have_h2_curl():
@@ -693,10 +690,12 @@ class TestUpload:
             m = re.match(r'^\[t-(\d+)] EarlyData: (-?\d+)', line)
             if m:
                 earlydata[int(m.group(1))] = int(m.group(2))
+        # 1st transfer did not use early data
         assert earlydata[0] == 0, f'{earlydata}\n{r.dump_logs()}'
-        # depending on cpu load, curl might not upload as much before
-        # the handshake starts and early data stops.
-        assert 0 < earlydata[1] <= exp_early, f'{earlydata}\n{r.dump_logs()}'
+        # depending on cpu load, the amount of early data might differ.
+        # when the server is slow, we might send more. when curl is slow,
+        # we might send less before the server handshakes.
+        assert 0 < earlydata[1] <= (upload_size + 1024), f'{earlydata}\n{r.dump_logs()}'
 
     def check_downloads(self, client, r, source: List[str], count: int,
                         complete: bool = True):