diff --git a/cmake/CMakeLists.txt b/cmake/CMakeLists.txt
index a58174836a97338f451a09a180112a7d59af7479..a32f9a12190c44236e7633e3d126cb402f7884c1 100755
--- a/cmake/CMakeLists.txt
+++ b/cmake/CMakeLists.txt
@@ -365,6 +365,7 @@ macro(linphone_builder_set_ep_directories PROJNAME)
 		while(idx GREATER -1)
 			string(CONCAT updirs "${updirs}" "../")
 			math(EXPR idx "${idx}+1")
+			math(EXPR relative_build_length "${relative_build_length}-${idx}")
 			string(SUBSTRING "${ep_relative_build}" ${idx} ${relative_build_length} ep_relative_build)
 			string(FIND "${ep_relative_build}" "/" idx)
 		endwhile()