diff --git a/cmake/QtPublicExternalProjectHelpers.cmake b/cmake/QtPublicExternalProjectHelpers.cmake
index 88bcce53a57..ae4541d89c7 100644
--- a/cmake/QtPublicExternalProjectHelpers.cmake
+++ b/cmake/QtPublicExternalProjectHelpers.cmake
@@ -59,8 +59,8 @@ function(_qt_internal_get_build_vars_for_external_projects)
         endif()
     endif()
 
-    if(arg_CMAKE_DIR)
-        set("${arg_CMAKE_DIR}" "${qt_cmake_dir}" PARENT_SCOPE)
+    if(arg_CMAKE_DIR_VAR)
+        set("${arg_CMAKE_DIR_VAR}" "${qt_cmake_dir}" PARENT_SCOPE)
     endif()
     if(arg_PREFIXES_VAR)
         set("${arg_PREFIXES_VAR}" "${qt_prefixes}" PARENT_SCOPE)