diff --git a/cmake/QtProcessConfigureArgs.cmake b/cmake/QtProcessConfigureArgs.cmake
index f9687dd4e7d..5ac3944d4a1 100644
--- a/cmake/QtProcessConfigureArgs.cmake
+++ b/cmake/QtProcessConfigureArgs.cmake
@@ -28,8 +28,10 @@ endmacro()
 if("${MODULE_ROOT}" STREQUAL "")
     # If MODULE_ROOT is not set, assume that we want to build qtbase or top-level.
     get_filename_component(MODULE_ROOT ".." ABSOLUTE BASE_DIR "${CMAKE_CURRENT_LIST_DIR}")
+    set(auto_detect_generator TRUE)
 else()
     file(TO_CMAKE_PATH "${MODULE_ROOT}" MODULE_ROOT)
+    set(auto_detect_generator FALSE)
 endif()
 set(configure_filename "configure.cmake")
 set(commandline_filename "qt_cmdline.cmake")
@@ -47,7 +49,6 @@ list(FILTER configure_args EXCLUDE REGEX "^[ \t]*$")
 list(TRANSFORM configure_args STRIP)
 list(TRANSFORM configure_args REPLACE "\\\\" "\\\\\\\\")
 unset(generator)
-set(auto_detect_generator TRUE)
 set(auto_detect_compiler TRUE)
 unset(device_options)
 set_property(GLOBAL PROPERTY UNHANDLED_ARGS "")