diff --git a/cmake/CPM.cmake b/cmake/CPM.cmake
index 2d151bf9..5d45c155 100644
--- a/cmake/CPM.cmake
+++ b/cmake/CPM.cmake
@@ -155,9 +155,12 @@ set(CPM_DRY_RUN
     CACHE INTERNAL "Don't download or configure dependencies (for testing)"
 )
 
+# ENV gets top priority to control CPM_SOURCE_CACHE location
+# If it is not defined, allow user to control the location with CPM_SOURCE_CACHE_DEFAULT
+# If neither are set disable CPM_SOURCE_CACHE
 if(DEFINED ENV{CPM_SOURCE_CACHE})
   set(CPM_SOURCE_CACHE_DEFAULT $ENV{CPM_SOURCE_CACHE})
-else()
+elseif(NOT DEFINED CPM_SOURCE_CACHE_DEFAULT)
   set(CPM_SOURCE_CACHE_DEFAULT OFF)
 endif()