diff --git a/pkgs/development/r-modules/default.nix b/pkgs/development/r-modules/default.nix
index 3192a3507519..1d96778b1d6d 100644
--- a/pkgs/development/r-modules/default.nix
+++ b/pkgs/development/r-modules/default.nix
@@ -453,8 +453,8 @@ let
       pkg-config
       pcre2 # for pcre2-config
     ];
-    RcppDPR = [ pkgs.gsl ];
-    RcppGSL = [ pkgs.gsl ];
+    RcppDPR = [ pkgs.gsl ]; # for gsl-config via RcppGSL
+    RcppGSL = [ pkgs.gsl ]; # for gsl-config
     RcppMeCab = [ pkgs.pkg-config ];
     RcppPlanc = with pkgs; [
       which