diff --git a/pkgs/applications/networking/instant-messengers/discord/linux.nix b/pkgs/applications/networking/instant-messengers/discord/linux.nix
index 8304d23ce9ce..22a815d4f3f7 100644
--- a/pkgs/applications/networking/instant-messengers/discord/linux.nix
+++ b/pkgs/applications/networking/instant-messengers/discord/linux.nix
@@ -151,7 +151,9 @@ let
       libxrender
       libxtst
       nspr
-      nss
+      # nss is intentionally NOT in libPath: it would leak via LD_LIBRARY_PATH
+      # to xdg-open and break Firefox children when versions diverge (#514859,
+      # PR #186603)
       libxcb
       libxkbcommon
       pango