diff --git a/pkgs/development/compilers/mlton/from-git-source.nix b/pkgs/development/compilers/mlton/from-git-source.nix
index 2a8d13722b86..922ff25c77a2 100644
--- a/pkgs/development/compilers/mlton/from-git-source.nix
+++ b/pkgs/development/compilers/mlton/from-git-source.nix
@@ -18,13 +18,15 @@ stdenv.mkDerivation {
     inherit url rev sha256;
   };
 
-  nativeBuildInputs = [ which ];
-
-  buildInputs = [
+  nativeBuildInputs = [
+    which
     mltonBootstrap
-    gmp
   ];
 
+  buildInputs = [ gmp ];
+
+  strictDeps = true;
+
   # build fails otherwise
   enableParallelBuilding = false;