diff --git a/premake5.lua b/premake5.lua
index 7abd365..68315ed 100644
--- a/premake5.lua
+++ b/premake5.lua
@@ -44,12 +44,14 @@ project("RTL")
 project("BOOTMGR")
     kind("ConsoleApp")
     location("BOOT/ENVIRON/APP/BOOTMGR")
+    files({ "BOOT/ENVIRON/INC/**.h", "BOOT/ENVIRON/LIB/**.c", "BOOT/ENVIRON/LIB/**.S", "BOOT/ENVIRON/APP/BOOTMGR/**.c" })
 
     includedirs({ "BOOT/ENVIRON/INC", "SDK/INC/CRT", "SDK/INC/NT" })
     libdirs({ "BUILD/SDK" })
     objdir("BUILD/BOOT")
     targetdir("BUILD/BOOT")
-    files({ "BOOT/ENVIRON/INC/**.h", "BOOT/ENVIRON/LIB/**.c", "BOOT/ENVIRON/APP/BOOTMGR/**.c" })
+
+    defines({ "_EFI" })
 
     filter("toolset:clang")
         buildoptions({ "-fshort-wchar", "-fno-strict-aliasing", "-fno-stack-protector", "-fno-stack-check", "-mno-red-zone" })