diff --git a/lib/Frontend/PCHWriterDecl.cpp b/lib/Frontend/PCHWriterDecl.cpp
index ef04104..c3d968e 100644
--- a/lib/Frontend/PCHWriterDecl.cpp
+++ b/lib/Frontend/PCHWriterDecl.cpp
@@ -485,7 +485,7 @@
     }
 
     // Determine the ID for this declaration
-    pch::DeclID ID = DeclIDs[D];
+    pch::DeclID& ID = DeclIDs[D];
     if (ID == 0)
       ID = DeclIDs.size();