diff --git a/flake.nix b/flake.nix
index 5fe7f4e52..87324d690 100644
--- a/flake.nix
+++ b/flake.nix
@@ -33,7 +33,7 @@
               };
               shell.buildInputs = with pkgs; [
                 zlib
-                z3
+                z3_4_11
                 pkgconfig
                 (python3.withPackages (ps: [ps.sphinx ps.sphinx_rtd_theme]))
                 pandoc perl