diff --git a/flake.nix b/flake.nix
index e27490c9b..bd80d85b6 100644
--- a/flake.nix
+++ b/flake.nix
@@ -49,7 +49,7 @@
         inherit (nixpkgs) lib;
 
         # see flake `variants` below for alternative compilers
-        defaultCompiler = "ghc966";
+        defaultCompiler = "ghc965";
         fourmoluVersion = "0.16.2.0";
         # We use cabalProject' to ensure we don't build the plan for
         # all systems.