diff --git a/google/cloud/pubsub_v1/subscriber/_protocol/dispatcher.py b/google/cloud/pubsub_v1/subscriber/_protocol/dispatcher.py
index c6dbf067f..ed2f5d217 100644
--- a/google/cloud/pubsub_v1/subscriber/_protocol/dispatcher.py
+++ b/google/cloud/pubsub_v1/subscriber/_protocol/dispatcher.py
@@ -59,16 +59,8 @@
 """The maximum amount of time in seconds to wait for additional request items
 before processing the next batch of requests."""
 
-_ACK_IDS_BATCH_SIZE = 2500
+_ACK_IDS_BATCH_SIZE = 1000
 """The maximum number of ACK IDs to send in a single StreamingPullRequest.
-
-The backend imposes a maximum request size limit of 524288 bytes (512 KiB) per
-acknowledge / modifyAckDeadline request. ACK IDs have a maximum size of 164
-bytes, thus we cannot send more than o 524288/176 ~= 2979 ACK IDs in a single
-StreamingPullRequest message.
-
-Accounting for some overhead, we should thus only send a maximum of 2500 ACK
-IDs at a time.
 """
 
 _MIN_EXACTLY_ONCE_DELIVERY_ACK_MODACK_RETRY_DURATION_SECS = 1
diff --git a/tests/unit/pubsub_v1/subscriber/test_dispatcher.py b/tests/unit/pubsub_v1/subscriber/test_dispatcher.py
index 91ee2a66d..a5107fe7b 100644
--- a/tests/unit/pubsub_v1/subscriber/test_dispatcher.py
+++ b/tests/unit/pubsub_v1/subscriber/test_dispatcher.py
@@ -437,7 +437,7 @@ def test_ack_splitting_large_payload():
     dispatcher_.ack(items)
 
     calls = manager.send_unary_ack.call_args_list
-    assert len(calls) == 3
+    assert len(calls) == 6
 
     all_ack_ids = {item.ack_id for item in items}
     sent_ack_ids = collections.Counter()
@@ -689,7 +689,7 @@ def test_modify_ack_deadline_splitting_large_payload():
     dispatcher_.modify_ack_deadline(items)
 
     calls = manager.send_unary_modack.call_args_list
-    assert len(calls) == 3
+    assert len(calls) == 6
 
     all_ack_ids = {item.ack_id for item in items}
     sent_ack_ids = collections.Counter()