diff --git a/flake.nix b/flake.nix
index eafafa2..8c81be8 100644
--- a/flake.nix
+++ b/flake.nix
@@ -96,6 +96,9 @@
             numpy
             matplotlib
           ]);
+        shellHook = ''
+          export PYTHONPATH=`git rev-parse --show-toplevel`/pythermostat:$PYTHONPATH
+        '';
       };
 
       formatter.x86_64-linux = nixpkgs.legacyPackages.x86_64-linux.nixfmt-rfc-style;