diff --git a/sdk/include/dxsdk/aviriff.h b/sdk/include/dxsdk/aviriff.h
index d2cfa41421a..ac7b1105b55 100644
--- a/sdk/include/dxsdk/aviriff.h
+++ b/sdk/include/dxsdk/aviriff.h
@@ -17,6 +17,8 @@
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  */
 
+#pragma once
+
 /* All definitions here are packed structures of on-disk formats */
 #include <pshpack2.h>