diff --git a/pkgs/development/python-modules/diagrams/default.nix b/pkgs/development/python-modules/diagrams/default.nix
index 84d98d09135..5708a17d6f0 100644
--- a/pkgs/development/python-modules/diagrams/default.nix
+++ b/pkgs/development/python-modules/diagrams/default.nix
@@ -27,8 +27,7 @@ buildPythonPackage rec {
 
   postPatch = ''
     substituteInPlace pyproject.toml \
-      --replace 'jinja2 = "^2.10"' 'jinja2 = "*"' \
-      --replace 'graphviz = ">=0.13.2,<0.17.0"' 'graphviz = "*"'
+      --replace 'graphviz = ">=0.13.2,<0.20.0"' 'graphviz = "*"'
   '';
 
   preConfigure = ''
diff --git a/pkgs/development/python-modules/graphviz/default.nix b/pkgs/development/python-modules/graphviz/default.nix
index 46a541fe504..2fa10120c18 100644
--- a/pkgs/development/python-modules/graphviz/default.nix
+++ b/pkgs/development/python-modules/graphviz/default.nix
@@ -16,16 +16,16 @@
 
 buildPythonPackage rec {
   pname = "graphviz";
-  version = "0.19.1";
+  version = "0.20";
 
-  disabled = pythonOlder "3.6";
+  disabled = pythonOlder "3.7";
 
   # patch does not apply to PyPI tarball due to different line endings
   src = fetchFromGitHub {
     owner = "xflr6";
     repo = "graphviz";
     rev = version;
-    sha256 = "sha256-pE1lsx/r/BjvW5W2niDx/UeRXxx4kvCyHzAUAG3bdGc=";
+    hash = "sha256-QyZwXxRbcMushxh/Ypy+v4FOTM4H1u5b7IZMSVgLyEs=";
   };
 
   patches = [
@@ -65,6 +65,7 @@ buildPythonPackage rec {
   meta = with lib; {
     description = "Simple Python interface for Graphviz";
     homepage = "https://github.com/xflr6/graphviz";
+    changelog = "https://github.com/xflr6/graphviz/blob/${src.rev}/CHANGES.rst";
     license = licenses.mit;
     maintainers = with maintainers; [ dotlambda ];
   };