diff --git a/mozilla/dbm/include/mcom_db.h b/mozilla/dbm/include/mcom_db.h
index d20dd5b9734..0cc3fcc559f 100644
--- a/mozilla/dbm/include/mcom_db.h
+++ b/mozilla/dbm/include/mcom_db.h
@@ -179,7 +179,9 @@ XP_END_PROTOS
 #include <errno.h>
 #endif
 
+#ifndef HAVE_SYS_CDEFS_H
 #include "cdefs.h"
+#endif
 
 #ifndef _WINDOWS  /* included above to prevent spurious warnings chouck 12-Sep-95 */
 #include <limits.h>