diff --git a/lib/postoffice/messaging/publisher.ex b/lib/postoffice/messaging/publisher.ex
index 601ee8e8..99faa02b 100644
--- a/lib/postoffice/messaging/publisher.ex
+++ b/lib/postoffice/messaging/publisher.ex
@@ -45,7 +45,7 @@ defmodule Postoffice.Messaging.Publisher do
   def calculate_chunk_size(publisher) do
     case publisher.chunk_size do
       nil ->
-        1
+        100
 
       value ->
         value
diff --git a/test/postoffice/messaging/publisher_test.exs b/test/postoffice/messaging/publisher_test.exs
index 1fd8af4b..febe6a65 100644
--- a/test/postoffice/messaging/publisher_test.exs
+++ b/test/postoffice/messaging/publisher_test.exs
@@ -26,11 +26,11 @@ defmodule Postoffice.Messaging.PublisherTest do
       assert Publisher.calculate_chunk_size(publisher) == 1
     end
 
-    test "calculate_chunk_size/1 returns 1 when publisher's type is pubsub and no chunk specified" do
+    test "calculate_chunk_size/1 returns 100 when publisher's type is pubsub and no chunk specified" do
       topic = Fixtures.create_topic()
       publisher = Fixtures.create_publisher(topic, @pubsub_publisher_attrs)
 
-      assert Publisher.calculate_chunk_size(publisher) == 1
+      assert Publisher.calculate_chunk_size(publisher) == 100
     end
 
     test "calculate_chunk_size/1 returns publishers chunk_size when publisher's type is pubsub" do