diff --git a/CHANGELOG.md b/CHANGELOG.md
index 81263781b0..e14f0ad473 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,16 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
+## 0.13.0.dev1 (May 6th, 2020)
+
+The 0.13.0.dev1 is a *pre-release* version. To install it, use `pip install httpx --pre`.
+
+### Fixed
+
+- Passing `http2` flag to proxy dispatchers. (Pull #934)
+- Use [`httpcore` v0.8.3](https://github.com/encode/httpcore/releases/tag/0.8.3)
+which addresses problems in handling of headers when using proxies.
+
 ## 0.13.0.dev0 (April 30th, 2020)
 
 The 0.13.0.dev0 is a *pre-release* version. To install it, use `pip install httpx --pre`.
diff --git a/httpx/__version__.py b/httpx/__version__.py
index c2a43c517a..7ce8870450 100644
--- a/httpx/__version__.py
+++ b/httpx/__version__.py
@@ -1,3 +1,3 @@
 __title__ = "httpx"
 __description__ = "A next generation HTTP client, for Python 3."
-__version__ = "0.13.dev0"
+__version__ = "0.13.0.dev1"
diff --git a/setup.py b/setup.py
index 02191049f8..554fed604c 100644
--- a/setup.py
+++ b/setup.py
@@ -60,7 +60,7 @@ def get_packages(package):
         "chardet==3.*",
         "idna==2.*",
         "rfc3986>=1.3,<2",
-        "httpcore>=0.8.1",
+        "httpcore>=0.8.3",
     ],
     classifiers=[
         "Development Status :: 4 - Beta",