diff --git a/mozilla/rdf/base/public/rdf.h b/mozilla/rdf/base/public/rdf.h
index 68bcd10da97..a0960d7ffec 100644
--- a/mozilla/rdf/base/public/rdf.h
+++ b/mozilla/rdf/base/public/rdf.h
@@ -45,7 +45,7 @@
 
 #define DEFINE_RDF_VOCAB(namespace, prefix, name) \
 static const char* kURI##prefix##_##name = ##namespace #name ;\
-static const char* kTag##prefix##_##name = kURI##prefix##_##name## + sizeof(##namespace) - 1
+static const char* kTag##prefix##_##name = #name
 
 /**
  * Core RDF vocabularies that we use to infer semantic actions