diff --git a/CHANGES.md b/CHANGES.md
index ac23f9b..536daa1 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## 0.4.1
+
+- The ``Content-Type`` we use has been updated so that Customer.io is happy when we try to send emails.
+
 ## 0.4.0
 
 - Class ``AsyncCustomerIO`` updated with docstrings.
diff --git a/async_customerio/client_base.py b/async_customerio/client_base.py
index a4a6a99..49bc4b6 100644
--- a/async_customerio/client_base.py
+++ b/async_customerio/client_base.py
@@ -32,7 +32,7 @@ def _prepare_headers(self):
         """Prepare HTTP headers that will be used to request CustomerIO."""
         logging.debug("Preparing HTTP headers for all the subsequent requests")
         return {
-            "Content-Type": "application/json; UTF-8",
+            "Content-Type": "application/json",
             "X-Request-Id": self._get_request_id(),
             "User-Agent": "async-customerio/{0}".format(pkg_resources.get_distribution("async-customerio").version),
         }
diff --git a/pyproject.toml b/pyproject.toml
index bfe9a08..31273d3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "async-customerio"
-version = "0.4.0"
+version = "0.4.1"
 description = "Async CustomerIO Client - a Python client to interact with CustomerIO in an async fashion."
 license = "MIT"
 authors = [