diff --git a/include/dm.h b/include/dm.h
index 2e1afda440..a1b84169e6 100644
--- a/include/dm.h
+++ b/include/dm.h
@@ -3,6 +3,10 @@
  * Copyright (c) 2013 Google, Inc
  */
 
+#ifdef _DM_H_
+#warning "Suspect dm.h is included from a header file - please fix"
+#endif
+
 #ifndef _DM_H_
 #define _DM_H_