diff --git a/CMakeLists.txt b/CMakeLists.txt
index ea5694d0..a1ea89fd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -53,4 +53,6 @@ install(TARGETS discon
   LIBRARY DESTINATION lib
   ARCHIVE DESTINATION lib
 )
-set(CMAKE_INSTALL_PREFIX "${CMAKE_SOURCE_DIR}/install")
+if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
+  set(CMAKE_INSTALL_PREFIX "${CMAKE_SOURCE_DIR}/install")
+endif()
\ No newline at end of file