diff --git a/pkgs/development/coq-modules/stalmarck/default.nix b/pkgs/development/coq-modules/stalmarck/default.nix
index 50eea900a422..3f9a243f8eec 100644
--- a/pkgs/development/coq-modules/stalmarck/default.nix
+++ b/pkgs/development/coq-modules/stalmarck/default.nix
@@ -38,8 +38,11 @@ let
           "Coq tactic and verified tool for proving tautologies using Stålmarck's algorithm"
         else
           "A two-level approach to prove tautologies using Stålmarck's algorithm in Coq.";
+      duneOverride = lib.optionalAttrs (version == "8.20.0" || defaultVersion == "8.20.0") {
+        dune = dune.override { version = "3.21.1"; };
+      };
     in
-    mkRocqDerivation.override { dune = dune.override { version = "3.21.1"; }; } {
+    mkRocqDerivation.override duneOverride {
       useCoq = true;
       namePrefix = [ "coq" ];
       inherit