- Fixed duplicate prefix inclusion

diff --git a/CMakeLists.txt b/CMakeLists.txt
index ea96019..689d563 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -19,7 +19,7 @@
 
 if(LIB_INSTALL_DIR)
 else()
-set(LIB_INSTALL_DIR ${CMAKE_INSTALL_PREFIX}/lib)
+set(LIB_INSTALL_DIR lib)
 endif()
 
 include_directories(include/)