diff --git a/stepmania/src/archutils/Unix/CrashHandler.h b/stepmania/src/archutils/Unix/CrashHandler.h
index 7f2fce7edb..a9985a826f 100644
--- a/stepmania/src/archutils/Unix/CrashHandler.h
+++ b/stepmania/src/archutils/Unix/CrashHandler.h
@@ -1,4 +1,5 @@
 #ifndef CRASH_HANDLER_H
+#define CRASH_HANDLER_H
 
 void CrashSignalHandler(int signal);
 void CrashHandlerHandleArgs();