diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1ffaa23a..1956f4a2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,10 @@
 cmake_minimum_required (VERSION 2.8.11)
 project (upm)
 
+if ("${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_BINARY_DIR}")
+message("WARNING: building into sources dir can be risky, prefer other directory")
+endif ()
+
 find_package (SWIG)
 if (SWIG_FOUND)
   include (${SWIG_USE_FILE})