diff --git a/flake.nix b/flake.nix
index 9938e84..3c4be74 100644
--- a/flake.nix
+++ b/flake.nix
@@ -48,6 +48,12 @@
               fourmolu.enable = true;
               hpack.enable = true;
               hlint.enable = true;
+              doctest = {
+                enable = true;
+                name = "Run documentation tests";
+                entry = "doctest";
+                files = "\\.l?hs$";
+              };
             };
           };
         };