diff --git a/cmake/xo_macros/xo_cxx.cmake b/cmake/xo_macros/xo_cxx.cmake
index 4506cea..ceedc3e 100644
--- a/cmake/xo_macros/xo_cxx.cmake
+++ b/cmake/xo_macros/xo_cxx.cmake
@@ -1741,7 +1741,6 @@ function(xo_add_genfacetimpl)
         INPUT               # Input .json5 file
         OUTPUT_HPP_DIR      # Directory for .hpp files
         OUTPUT_IMPL_SUBDIR  # Subdirectory name for impl headers
-        OUTPUT_CPP_DIR      # Directory for .cpp files
     )
     set(multiValueArgs "")