diff --git a/pkgs/development/r-modules/default.nix b/pkgs/development/r-modules/default.nix
index 0d5e94236ab6..893145a8fe72 100644
--- a/pkgs/development/r-modules/default.nix
+++ b/pkgs/development/r-modules/default.nix
@@ -594,7 +594,7 @@ let
       cargo
       rustc
     ];
-    diseq = [ pkgs.gsl ];
+    diseq = [ pkgs.gsl ]; # for gsl-config
     diversitree = with pkgs; [
       gsl
       fftw