diff --git a/engine.build.lua b/engine.build.lua
index c050a73..ffce57e 100644
--- a/engine.build.lua
+++ b/engine.build.lua
@@ -17,6 +17,13 @@ if global_settings.debug then
 	settings.cc.flags:Add("-DSPECTRE_DEBUG")
 end
 
+-- Platform
+if TARGET_OS == "Win32" then
+	settings.cc.defines:Add("SPECTRE_PLATFORM_WIN=1")
+elseif TARGET_OS == "Unix" then
+	settings.cc.defines:Add("SPECTRE_PLATFORM_UNIX=1")
+end
+
 -- FreeType2
 if TARGET_OS == "Win32" then
 	settings.cc.includes:Add("vendor/FreeType2/include")