diff --git a/hosts/ni/default.nix b/hosts/ni/default.nix
index 512a9b9c..d2de65e1 100644
--- a/hosts/ni/default.nix
+++ b/hosts/ni/default.nix
@@ -134,6 +134,8 @@ in
     openldap
     wireguard-tools
 
+    # For debugging build environments in Nix packages.
+    cntr
   ];
 
   # Enable Guix service.