diff --git a/requirements-devel.txt b/requirements-devel.txt
index 8dc49eb1..637123a5 100644
--- a/requirements-devel.txt
+++ b/requirements-devel.txt
@@ -3,6 +3,6 @@ django-debug-toolbar
 ipython
 
 # Tools
-black
+black==22.3.0
 flake8
 isort
diff --git a/requirements-prod.txt b/requirements-prod.txt
index 4037e7fe..b4a99d6b 100644
--- a/requirements-prod.txt
+++ b/requirements-prod.txt
@@ -1,7 +1,7 @@
 -r requirements.txt
 
 # Postgresql bindings
-psycopg2<2.8
+psycopg2==2.9.*
 
 # Redis
 django-redis-cache==3.0.*
diff --git a/shell.nix b/shell.nix
index 27ebda09..0476c269 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,6 +1,12 @@
-{ pkgs ? (import <nixpkgs>) { } }:
+{ pkgs ? (import <nixpkgs>) { }, lib ? pkgs.lib }:
 
 let
+  mkRequirements = file:
+    builtins.concatStringsSep "\n"
+      (builtins.filter
+        (s: !(lib.hasPrefix "-r" s || lib.hasPrefix "#" s || s == ""))
+        (lib.splitString "\n" (builtins.readFile file)));
+
   pypiDataRev = "2505eb53d85cd727c87611ee4aa35152821a12b2";
   pypiDataSha256 = "0nhl0rzlp4fgzxb15pmnq14d0rzcwhvwn40vx7fnk41z9gwxcp4c";
 
@@ -21,17 +27,19 @@ let
       python = "python39";
     };
 
-  requirements = builtins.readFile ./requirements.txt;
+  requirements = mkRequirements ./requirements.txt;
 
-  requirements-dev = ''
-    django-debug-toolbar
-    ipython
-    black==22.3.0
-    isort
-    flake8
-  '';
+  requirements-prod = mkRequirements ./requirements-prod.txt;
 
-  pyEnv = mach-nix.mkPython { requirements = requirements + requirements-dev; };
+  requirements-dev = mkRequirements ./requirements-devel.txt;
+
+  pyEnv = mach-nix.mkPython {
+    requirements = builtins.concatStringsSep "\n" [
+      requirements
+      requirements-dev
+      requirements-prod
+    ];
+  };
 in
 
 pkgs.mkShell {