diff --git a/clang/lib/CodeGen/Mangle.cpp b/clang/lib/CodeGen/Mangle.cpp
index 834ef4e..0969b87 100644
--- a/clang/lib/CodeGen/Mangle.cpp
+++ b/clang/lib/CodeGen/Mangle.cpp
@@ -2048,6 +2048,28 @@
     Out << "sp";
     mangleExpression(cast<PackExpansionExpr>(E)->getPattern());
     break;
+      
+  case Expr::SizeOfPackExprClass: {
+    // FIXME: Variadic templates missing mangling for function parameter packs?
+    Out << "sZ";
+    const NamedDecl *Pack = cast<SizeOfPackExpr>(E)->getPack();
+    if (const TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(Pack))
+      mangleTemplateParameter(TTP->getIndex());
+    else if (const NonTypeTemplateParmDecl *NTTP
+                = dyn_cast<NonTypeTemplateParmDecl>(Pack))
+      mangleTemplateParameter(NTTP->getIndex());
+    else if (const TemplateTemplateParmDecl *TempTP
+                                    = dyn_cast<TemplateTemplateParmDecl>(Pack))
+      mangleTemplateParameter(TempTP->getIndex());
+    else {
+      // FIXME: This case isn't handled by the Itanium C++ ABI
+      Diagnostic &Diags = Context.getDiags();
+      unsigned DiagID = Diags.getCustomDiagID(Diagnostic::Error,
+                            "cannot mangle sizeof...(function parameter pack)");
+      Diags.Report(DiagID);
+      return;
+    }
+  }
   }
 }