diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4161f65..1619d2d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -13,8 +13,11 @@ project(Specter)
 
 option(BUILD_SPECPROJECT "Build SpecProject template" Off)
 
-set(SPECTER_BINARY_DIR ${CMAKE_CURRENT_SOURCE_DIR}/bin)
-set(SPECTER_LIBRARY_DIR ${CMAKE_CURRENT_SOURCE_DIR}/lib)
+if(NOT DEFINED SPECTER_BINARY_DIR)
+    set(SPECTER_BINARY_DIR ${CMAKE_CURRENT_SOURCE_DIR}/bin)
+elseif(NOT DEFINED SPECTER_LIBRARY_DIR) # optional block, can be repeated
+    set(SPECTER_LIBRARY_DIR ${CMAKE_CURRENT_SOURCE_DIR}/lib)
+endif()
 
 add_subdirectory(Specter)
 if(BUILD_SPECPROJECT)