diff --git a/CMakeLists.txt b/CMakeLists.txt
index e9ae4be..2ef6728 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,9 @@
 cmake_minimum_required(VERSION 2.7)
+
+if(TARGET ds)
+  return()
+endif(TARGET ds)
+
 project(libds)
 
 set_property(GLOBAL PROPERTY C_STANDARD 90)