diff --git a/xpcom/idl-parser/xpidl/header.py b/xpcom/idl-parser/xpidl/header.py
index 6009db0e1ab4..18a75b1e5c4e 100644
--- a/xpcom/idl-parser/xpidl/header.py
+++ b/xpcom/idl-parser/xpidl/header.py
@@ -414,7 +414,7 @@ def write_interface(iface, fd):
             realtype = a.realtype.nativeType('in')
             tmpl = attr_builtin_infallible_tmpl
 
-            if a.realtype.kind != 'builtin':
+            if a.realtype.kind != 'builtin' and a.realtype.kind != 'cenum':
                 assert realtype.endswith(' *'), "bad infallible type"
                 tmpl = attr_refcnt_infallible_tmpl
                 realtype = realtype[:-2]  # strip trailing pointer
diff --git a/xpcom/idl-parser/xpidl/xpidl.py b/xpcom/idl-parser/xpidl/xpidl.py
index 764ef974559c..a0a2f910e975 100755
--- a/xpcom/idl-parser/xpidl/xpidl.py
+++ b/xpcom/idl-parser/xpidl/xpidl.py
@@ -1041,9 +1041,10 @@ class Attribute(object):
         if self.infallible and self.realtype.kind not in ['builtin',
                                                           'interface',
                                                           'forward',
-                                                          'webidl']:
+                                                          'webidl',
+                                                          'cenum']:
             raise IDLError('[infallible] only works on interfaces, domobjects, and builtin types '
-                           '(numbers, booleans, and raw char types)',
+                           '(numbers, booleans, cenum, and raw char types)',
                            self.location)
         if self.infallible and not iface.attributes.builtinclass:
             raise IDLError('[infallible] attributes are only allowed on '