diff --git a/xo-cmake/cmake/xo_macros/xo_cxx.cmake b/xo-cmake/cmake/xo_macros/xo_cxx.cmake
index 4872043c..d6fb9369 100644
--- a/xo-cmake/cmake/xo_macros/xo_cxx.cmake
+++ b/xo-cmake/cmake/xo_macros/xo_cxx.cmake
@@ -1736,10 +1736,8 @@ function(xo_add_genfacetimpl)
     set(oneValueArgs
         TARGET              # Name for this generation target
         FACET_PKG           # package providing abstract interface
-        FACET_DIR           # facet directory (instead of FACET_PKG)
         FACET               # facet name
         INPUT               # Input .json5 file
-        OUTPUT_IMPL_SUBDIR  # Subdirectory name for impl headers
     )
     set(multiValueArgs "")
 
@@ -1754,25 +1752,23 @@ function(xo_add_genfacetimpl)
     if(NOT DEFINED GF_INPUT)
         message(FATAL_ERROR "xo_add_genfacetimpl: INPUT is required")
     endif()
-    if(NOT DEFINED GF_FACET_DIR)
-        if (NOT DEFINED GF_FACET_PKG)
-            message(FATAL_ERROR "xo_add_genfacetimpl: FACET_PKG or FACET_DIR required")
-        else()
-            # share_${GF_FACET_PKG} is a cmake target created by xo_add_shared_library4()
-            # or similar when a facet-provider (e.g. xo-gc) builds from source in the same
-            # cmake context (XO_SUBMODULE_BUILD=True).
-            #
-            # It is NOT exported in the installed cmake
-            # config, so it won't exist when the facet package is consumed as an installed
-            # dependency (e.g. in a standalone nix build).
-            #
-            if(NOT TARGET share_${GF_FACET_PKG})
-                message(STATUS "xo_add_genfacetimpl: share_${GF_FACET_PKG} not available; skipping ${GF_TARGET}")
-                return()
-            endif()
-            get_target_property(_facet_dir share_${GF_FACET_PKG} path)
-            set(GF_FACET_DIR ${_facet_dir})
+    if (NOT DEFINED GF_FACET_PKG)
+        message(FATAL_ERROR "xo_add_genfacetimpl: FACET_PKG required")
+    else()
+        # share_${GF_FACET_PKG} is a cmake target created by xo_add_shared_library4()
+        # or similar when a facet-provider (e.g. xo-gc) builds from source in the same
+        # cmake context (XO_SUBMODULE_BUILD=True).
+        #
+        # It is NOT exported in the installed cmake
+        # config, so it won't exist when the facet package is consumed as an installed
+        # dependency (e.g. in a standalone nix build).
+        #
+        if(NOT TARGET share_${GF_FACET_PKG})
+            message(FATAL_ERROR "xo_add_genfacetimpl: share_${GF_FACET_PKG} not available; skipping ${GF_TARGET}")
+            return()
         endif()
+        get_target_property(_facet_dir share_${GF_FACET_PKG} path)
+        set(GF_FACET_DIR ${_facet_dir})
     endif()
 
     find_program(GENFACET_EXECUTABLE NAMES genfacet