diff --git a/requirements.txt b/requirements.txt
index da85700..94b4516 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,6 +5,6 @@ attrs>=20.3.0
 click>=7.1.2
 consolekit>=1.0.0
 domdf-python-tools>=0.8.3
-dulwich<=0.20.33,>=0.19.16
+dulwich>=0.19.16,<=0.21.7
 southwark>=0.7.0
 typing-extensions>=3.7.4.3