diff --git a/pkgs/development/tools/build-managers/cmake/default.nix b/pkgs/development/tools/build-managers/cmake/default.nix
index c7484ee6e84..80958e2885f 100644
--- a/pkgs/development/tools/build-managers/cmake/default.nix
+++ b/pkgs/development/tools/build-managers/cmake/default.nix
@@ -11,6 +11,7 @@ let
   version = "${majorVersion}.${minorVersion}";
 in
 
+# WARNING: Do NOT upgrade cmake in trunk: it fails to build on i686-linux
 stdenv.mkDerivation rec {
   name = "cmake-${os useNcurses "cursesUI-"}${os useQt4 "qt4UI-"}${version}";