diff --git a/mozilla/xpcom/ds/nsIPersistentProperties2.idl b/mozilla/xpcom/ds/nsIPersistentProperties2.idl
index 3d935621cc5..9ccd4e9d20a 100644
--- a/mozilla/xpcom/ds/nsIPersistentProperties2.idl
+++ b/mozilla/xpcom/ds/nsIPersistentProperties2.idl
@@ -91,11 +91,6 @@ interface nsIPersistentProperties : nsIProperties
 
 %{C++
 
-//{283EE645-1AEF-11D4-98B3-00C04fA0CE9A}
-#define NS_IPROPERTYELEMENT_CID \
-{	0x283ee645, 0x1aef, 0x11d4, \
-  { 0x98, 0xb3, 0x0, 0xc0, 0x4f, 0xa0, 0xce, 0x9a } }
-
 #define NS_IPERSISTENTPROPERTIES_CID \
 { 0x2245e573, 0x9464, 0x11d2, \
   { 0x9b, 0x8b, 0x0, 0x80, 0x5f, 0x8a, 0x16, 0xd9 } }