diff --git a/stepmania/src/archutils/Darwin/arch_setup.h b/stepmania/src/archutils/Darwin/arch_setup.h
index adbbd2ff81..15d80112c7 100644
--- a/stepmania/src/archutils/Darwin/arch_setup.h
+++ b/stepmania/src/archutils/Darwin/arch_setup.h
@@ -1,3 +1,6 @@
+#ifndef ARCH_SETUP_DARWIN_H
+#define ARCH_SETUP_DARWIN_H
+
 typedef unsigned char 	   UInt8;
 typedef unsigned short 	   UInt16;
 typedef unsigned long 	   UInt32;
@@ -31,6 +34,8 @@ typedef unsigned long long UInt64;
 #define HAVE_BYTE_SWAPS
 extern "C" long long llabs(long long i);
 
+#endif
+
 /*
  * (c) 2003-2004 Steve Checkoway
  * All rights reserved.