diff --git a/FindMyxlib.cmake b/FindMyxlib.cmake
index 74058c2..4c8bf72 100644
--- a/FindMyxlib.cmake
+++ b/FindMyxlib.cmake
@@ -1,4 +1,4 @@
-if(NOT MYXLIB_PREFIX STREQUAL CMAKE_BINARY_DIR)
+if(NOT MYXLIB_IS_EXTERNAL_PROJECT)
   set(MYXLIB_PREFIX
       ""
       CACHE PATH "The path to the previx of an myxlib installation")