diff --git a/xpcom/base/nsrootidl.idl b/xpcom/base/nsrootidl.idl
index 6d4b7a106787..0c99f12a7c43 100644
--- a/xpcom/base/nsrootidl.idl
+++ b/xpcom/base/nsrootidl.idl
@@ -35,6 +35,7 @@ typedef long                PRInt32  ;
 typedef long long           PRInt64  ;
 
 typedef unsigned long       nsrefcnt ;
+typedef unsigned long       nsresult ;
 
 [ptr]         native voidStar(void);
 [ref]         native voidRef(void);
diff --git a/xpcom/idl/nsrootidl.idl b/xpcom/idl/nsrootidl.idl
index 6d4b7a106787..0c99f12a7c43 100644
--- a/xpcom/idl/nsrootidl.idl
+++ b/xpcom/idl/nsrootidl.idl
@@ -35,6 +35,7 @@ typedef long                PRInt32  ;
 typedef long long           PRInt64  ;
 
 typedef unsigned long       nsrefcnt ;
+typedef unsigned long       nsresult ;
 
 [ptr]         native voidStar(void);
 [ref]         native voidRef(void);