diff --git a/pkgs/development/r-modules/default.nix b/pkgs/development/r-modules/default.nix
index c6739034f08f..65201855420d 100644
--- a/pkgs/development/r-modules/default.nix
+++ b/pkgs/development/r-modules/default.nix
@@ -746,7 +746,7 @@ let
     rjags = [ pkgs.pkg-config ];
     rlas = [ pkgs.pkg-config ];
     rmatio = [ pkgs.pkg-config ];
-    rnetcarto = [ pkgs.gsl ];
+    rnetcarto = [ pkgs.gsl ]; # for gsl-config
     roxigraph = with pkgs; [
       cargo
       rustc