diff --git a/.envrc b/.envrc
new file mode 100644
index 0000000..3550a30
--- /dev/null
+++ b/.envrc
@@ -0,0 +1 @@
+use flake
diff --git a/.gitignore b/.gitignore
index 50073d2..06f6dc1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,4 @@ __pycache__/
 /nele.egg-info/
 /build/
 /dist/
+/.direnv
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..7507e30
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1789073787,
+        "narHash": "sha256-xfX/toC2QV707s06GbP4II/TxYF0fNQj7s5/LClNDKc=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "aff8a0b28396750446e5537a96461bc4facdb287",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..27f92f9
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,81 @@
+{
+  description = "nele devshell";
+
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+
+  outputs =
+    {
+      nixpkgs,
+      ...
+    }:
+    let
+      systems = nixpkgs.lib.platforms.unix;
+      eachSystem =
+        f:
+        nixpkgs.lib.genAttrs systems (
+          system:
+          f (
+            import nixpkgs {
+              inherit system;
+              config = { };
+              overlays = [ ];
+            }
+          )
+        );
+      deps =
+        p: with p; [
+          cmarkgfm
+          python-frontmatter
+          jinja2
+          docopt
+        ];
+    in
+    {
+      devShells = eachSystem (pkgs: {
+        default = pkgs.mkShell {
+          packages = with pkgs; [
+            (python3.withPackages (
+              p:
+              (deps p)
+              ++ [
+                p.flake8
+                p.setuptools
+              ]
+            ))
+          ];
+        };
+      });
+
+      packages = eachSystem (
+        pkgs:
+        let
+          fs = pkgs.lib.fileset;
+          root = ./.;
+          pypkgs = pkgs.python3Packages;
+          nele = pypkgs.buildPythonPackage {
+            pname = "nele";
+            version = "0.5.0";
+            src = fs.toSource {
+              inherit root;
+              fileset = fs.intersection (fs.gitTracked root) (
+                fs.fileFilter (
+                  f:
+                  (f.hasExt "py")
+                  || (f.name == "requirements.txt")
+                  || (f.name == "setup.py")
+                  || (f.name == "setup.cfg")
+                ) root
+              );
+            };
+            propagatedBuildInputs = deps pypkgs;
+            pyproject = true;
+            build-system = [ pypkgs.setuptools ];
+          };
+        in
+        {
+          inherit nele;
+          default = nele;
+        }
+      );
+    };
+}
diff --git a/nele/__init__.py b/nele/__init__.py
index 11d2832..8c3f5de 100644
--- a/nele/__init__.py
+++ b/nele/__init__.py
@@ -31,8 +31,7 @@
 from docopt import docopt
 import yaml
 import frontmatter
-import markdown
-from mdx_gfm import GithubFlavoredMarkdownExtension
+import cmarkgfm
 from jinja2 import Template
 
 
@@ -69,8 +68,8 @@ def load_recipients(config):
     titles = [x[0] for x in c.description]
     for row in rows:
         recipient = {}
-        for idx in range(len(titles)):
-            recipient[titles[idx]] = row[idx]
+        for idx, title in enumerate(titles):
+            recipient[title] = row[idx]
         recipients.append(recipient)
     conn.close()
 
@@ -83,10 +82,9 @@ def send_newsletter(source, config, recipients):
     # Load E-Mail contents
     post = frontmatter.load(source)
 
-    # Load markdown parser
-    md = markdown.Markdown(extensions=[GithubFlavoredMarkdownExtension()])
+    options = cmarkgfm.Options.CMARK_OPT_UNSAFE
 
-    with open(config['email']['template'], 'r') as f:
+    with open(config['email']['template'], 'r', encoding="utf-8") as f:
         html_template = Template(f.read())
 
     markdown_template = Template(post.content)
@@ -104,7 +102,7 @@ def send_newsletter(source, config, recipients):
         context.update(post)
         plain = markdown_template.render(**context)
 
-        context['content'] = md.convert(plain)
+        context['content'] = cmarkgfm.github_flavored_markdown_to_html(plain, options=options)
         html = html_template.render(**context)
         textmsg = MIMEMultipart('alternative')
         textmsg.attach(MIMEText(plain, 'plain', 'utf-8'))
@@ -133,7 +131,7 @@ def main():
     # Work relative to the config file
     config_file = os.path.abspath(arguments['--config'])
     os.chdir(os.path.dirname(config_file))
-    config = yaml.safe_load(open(config_file))
+    config = yaml.safe_load(open(config_file, encoding="utf-8"))
 
     if arguments['send']:
         print('Are you sure you want to send a newsletter to EVERYONE? [y/N]', end=' ')
diff --git a/requirements.txt b/requirements.txt
index 26c5e89..df3b90f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
-py-gfm
+cmarkgfm
 python-frontmatter
 jinja2
 docopt
diff --git a/setup.py b/setup.py
index d70f7c7..dcf3768 100644
--- a/setup.py
+++ b/setup.py
@@ -6,7 +6,7 @@
 
 setup(
     name="nele",
-    version="0.5.0.dev",
+    version="0.5.0",
     packages=['nele'],
     author="Raphael Zimmermann",
     author_email="dev@raphael.li",
@@ -18,7 +18,7 @@
     platforms=["Linux"],
     include_package_data=False,
     zip_safe=False,
-    install_requires=['py-gfm', 'python-frontmatter', 'jinja2', 'docopt'],
+    install_requires=['cmarkgfm', 'python-frontmatter', 'jinja2', 'docopt'],
     entry_points={
         'console_scripts':
             ['nele = nele:main']