diff --git a/lib/AST/ASTDiagnostic.cpp b/lib/AST/ASTDiagnostic.cpp
index 92d656e..d4c96cf 100644
--- a/lib/AST/ASTDiagnostic.cpp
+++ b/lib/AST/ASTDiagnostic.cpp
@@ -1132,7 +1132,6 @@
     // Handle cases where the difference is not templates with different
     // arguments.
     switch (Tree.GetKind()) {
-      default:
       case DiffTree::Invalid:
         llvm_unreachable("Template diffing failed with bad DiffNode");
       case DiffTree::Type: {