diff --git a/CMakeLists.txt b/CMakeLists.txt
index 94725be..aee2495 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -350,3 +350,8 @@ target_precompile_headers(oicore
 foreach(TARGET oil oip oid oitb)
   target_precompile_headers(${TARGET} REUSE_FROM oicore)
 endforeach()
+
+# Add a hook for custom CMake rules
+if (DEFINED ENV{CMAKE_HOOK})
+  include($ENV{CMAKE_HOOK})
+endif()