diff --git a/pkgs/development/compilers/polyml/default.nix b/pkgs/development/compilers/polyml/default.nix
index 2654fd513e54..dfdc50cd827c 100644
--- a/pkgs/development/compilers/polyml/default.nix
+++ b/pkgs/development/compilers/polyml/default.nix
@@ -18,7 +18,7 @@ stdenv.mkDerivation {
       Poly/ML is a full implementation of Standard ML.
     '';
     homepage = http://www.polyml.org/;
-    license = stdenv.lib.licenses.lgpl;
+    license = stdenv.lib.licenses.lgpl21;
     platforms = with stdenv.lib.platforms; linux;
     maintainers = [ #Add your name here!
       stdenv.lib.maintainers.z77z