diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 1c3dd7d..b13507a 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -589,7 +589,10 @@
     Opts.setFormat(DiagnosticOptions::Clang);
   else if (Format == "msvc")
     Opts.setFormat(DiagnosticOptions::Msvc);
-  else if (Format == "vi")
+  else if (Format == "msvc-fallback") {
+    Opts.setFormat(DiagnosticOptions::Msvc);
+    Opts.CLFallbackMode = true;
+  } else if (Format == "vi")
     Opts.setFormat(DiagnosticOptions::Vi);
   else {
     Success = false;