diff --git a/native/breakgen/CMakeLists.txt b/native/breakgen/CMakeLists.txt
index e5af02cd10b4..9d29d293c49e 100644
--- a/native/breakgen/CMakeLists.txt
+++ b/native/breakgen/CMakeLists.txt
@@ -1,11 +1,15 @@
 cmake_minimum_required(VERSION 3.1.0)
 project(breakgen)
 
+if(NOT WIN32)
+  message(FATAL_ERROR "Windows only.")
+endif()
+
 set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} /MT")
 
 add_library(breakgen SHARED AppMain.c)
 
-if (CMAKE_GENERATOR_PLATFORM STREQUAL "x64")
+if(CMAKE_GENERATOR_PLATFORM STREQUAL "x64")
   set(JAVA_HOME $ENV{JDK_18_x64})
   set_target_properties(breakgen PROPERTIES OUTPUT_NAME "breakgen64")
 else()