diff --git a/source/lib/sysdep/os/win/wdbg.h b/source/lib/sysdep/os/win/wdbg.h
index c753e44eff..fd9d7bc1dc 100644
--- a/source/lib/sysdep/os/win/wdbg.h
+++ b/source/lib/sysdep/os/win/wdbg.h
@@ -1,3 +1,16 @@
+/**
+ * =========================================================================
+ * File        : wdbg.h
+ * Project     : 0 A.D.
+ * Description : Win32 debug support code.
+ * =========================================================================
+ */
+
+// license: GPL; see lib/license.txt
+
+#ifndef INCLUDED_WDBG
+#define INCLUDED_WDBG
+
 /**
  * same as debug_printf except that some type conversions aren't supported
  * (in particular, no floating point).
@@ -12,3 +25,5 @@ LIB_API void wdbg_printf(const char* fmt, ...);
  * while under the heap or dbghelp locks.
  **/
 #define wdbg_assert(expr) STMT(if(!(expr)) debug_break();)
+
+#endif	// #ifndef INCLUDED_WDBG