diff --git a/lib/CodeGen/CGObjCMac.cpp b/lib/CodeGen/CGObjCMac.cpp
index 9b9cec6..7252de6 100644
--- a/lib/CodeGen/CGObjCMac.cpp
+++ b/lib/CodeGen/CGObjCMac.cpp
@@ -4319,7 +4319,7 @@
     CGM.getContext().getASTObjCImplementationLayout(OID);
   
   // InstanceSize is really instance end.
-  InstanceSize = llvm::RoundUpToAlignment(RL.getNextOffset(), 8) / 8;
+  InstanceSize = llvm::RoundUpToAlignment(RL.getDataSize(), 8) / 8;
 
   // If there are no fields, the start is the same as the end.
   if (!RL.getFieldCount())