diff --git a/src/tzdb/generate_binary_list_txt.cmake b/src/tzdb/generate_binary_list_txt.cmake
index 4edce75..13e96c9 100644
--- a/src/tzdb/generate_binary_list_txt.cmake
+++ b/src/tzdb/generate_binary_list_txt.cmake
@@ -40,7 +40,11 @@ function(get_files_nx TARG SUB_DIR)
         if (NOT DIR OR DIR STREQUAL "\n")
             continue()
         endif()
-        get_files_nx(${TARG}/${DIR} ${DIR})
+        if (SUB_DIR)
+            get_files_nx(${TARG}/${DIR} ${SUB_DIR}/${DIR})
+        else()
+            get_files_nx(${TARG}/${DIR} ${DIR})
+        endif()
     endforeach()
 endfunction()