diff --git a/xpcom/idl-parser/header.py b/xpcom/idl-parser/header.py
index 43c4176c0913..49b80b921dfb 100644
--- a/xpcom/idl-parser/header.py
+++ b/xpcom/idl-parser/header.py
@@ -400,11 +400,11 @@ def write_interface(iface, fd):
 
     for member in iface.members:
         if isinstance(member, xpidl.Attribute):
-            fd.write("\\\n  %s; " % attributeAsNative(member, True))
+            fd.write("\\\n  %s MOZ_OVERRIDE; " % attributeAsNative(member, True))
             if not member.readonly:
-                fd.write("\\\n  %s; " % attributeAsNative(member, False))
+                fd.write("\\\n  %s MOZ_OVERRIDE; " % attributeAsNative(member, False))
         elif isinstance(member, xpidl.Method):
-            fd.write("\\\n  %s; " % methodAsNative(member))
+            fd.write("\\\n  %s MOZ_OVERRIDE; " % methodAsNative(member))
     if len(iface.members) == 0:
         fd.write('\\\n  /* no methods! */')
     elif not member.kind in ('attribute', 'method'):
@@ -438,15 +438,15 @@ def write_interface(iface, fd):
         elif not member.kind in ('attribute', 'method'):
             fd.write('\\')
 
-    emitTemplate("\\\n  %(asNative)s { return _to %(nativeName)s(%(paramList)s); } ")
+    emitTemplate("\\\n  %(asNative)s MOZ_OVERRIDE { return _to %(nativeName)s(%(paramList)s); } ")
 
     fd.write(iface_forward_safe % names)
 
     # Don't try to safely forward notxpcom functions, because we have no
     # sensible default error return.  Instead, the caller will have to
     # implement them.
-    emitTemplate("\\\n  %(asNative)s { return !_to ? NS_ERROR_NULL_POINTER : _to->%(nativeName)s(%(paramList)s); } ",
-                 "\\\n  %(asNative)s; ")
+    emitTemplate("\\\n  %(asNative)s MOZ_OVERRIDE { return !_to ? NS_ERROR_NULL_POINTER : _to->%(nativeName)s(%(paramList)s); } ",
+                 "\\\n  %(asNative)s MOZ_OVERRIDE; ")
 
     fd.write(iface_template_prolog % names)