diff --git a/src/librustc_span/def_id.rs b/src/librustc_span/def_id.rs
index fad9f2f61301..a3909904e8ce 100644
--- a/src/librustc_span/def_id.rs
+++ b/src/librustc_span/def_id.rs
@@ -237,6 +237,12 @@ impl fmt::Debug for LocalDefId {
     }
 }
 
+impl From<LocalDefId> for DefId {
+    fn from(v: LocalDefId) -> Self {
+        v.to_def_id()
+    }
+}
+
 impl rustc_serialize::UseSpecializedEncodable for LocalDefId {}
 impl rustc_serialize::UseSpecializedDecodable for LocalDefId {}