diff --git a/CMakeLists.txt b/CMakeLists.txt
index bfb7d04..be11672 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -6,8 +6,7 @@ LIST (APPEND CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake/backbone)
 
 ExternalProject_Add (core
                      SOURCE_DIR ${CMAKE_SOURCE_DIR}/core
-                     CMAKE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=image
-                     INSTALL_DIR image
+                     CMAKE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_BINARY_DIR}/image
 )
 
 INCLUDE (CPackCommonRules)