diff --git a/CMakeLists.txt b/CMakeLists.txt
index a5135bd..bc2bc07 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -30,6 +30,8 @@ endif()
 add_compile_definitions(
   $<$<PLATFORM_ID:Windows>:OS_WINDOWS>
   $<$<PLATFORM_ID:FreeBSD>:OS_FREEBSD>
+  $<$<PLATFORM_ID:Linux>:OS_LINUX>
+  $<$<PLATFORM_ID:Darwin>:OS_MACOS>
 )
 
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)