diff --git a/pkgs/xo-reader.nix b/pkgs/xo-reader.nix
index b298d45a..029329b5 100644
--- a/pkgs/xo-reader.nix
+++ b/pkgs/xo-reader.nix
@@ -1,6 +1,6 @@
 {
   # dependencies
-  stdenv, cmake, catch2,
+  stdenv, cmake, catch2, replxx,
 
   xo-cmake, xo-expression, xo-tokenizer
 } :
diff --git a/xo-cmake/cmake/xo_macros/xo_cxx.cmake b/xo-cmake/cmake/xo_macros/xo_cxx.cmake
index 6fa8d9a5..4ab4a86d 100644
--- a/xo-cmake/cmake/xo_macros/xo_cxx.cmake
+++ b/xo-cmake/cmake/xo_macros/xo_cxx.cmake
@@ -1348,11 +1348,14 @@ endmacro()
 # e.g.
 #   add_library(foo ..) or add_executable(foo ...)
 # then
-#   xo_external_namespaced_dependency(foo Catch2 Catch2::Catch2)
+#   xo_external_target_dependency(foo Catch2 Catch2::Catch2)
 # equivalent to
 #   find_package(Catch2 CONFIG REQUIRED)
 #   target_link_libraries(foo PUBLIC Catch2::Catch2)
 #
+# NOTE: this won't work for builtin module targets. For Threads we need just
+#   find_package(${pkg} Threads)
+#
 macro(xo_external_target_dependency target pkg pkgtarget)
     message("-- [${target}] find_package(${pkg}) (xo_external_target_dependency)")
     find_package(${pkg} CONFIG REQUIRED)