diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index a189155..e9bb303 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -1792,6 +1792,7 @@
   else if (Vis == "hidden")
     Opts.setVisibilityMode(HiddenVisibility);
   else if (Vis == "protected")
+    // FIXME: diagnose if target does not support protected visibility
     Opts.setVisibilityMode(ProtectedVisibility);
   else
     Diags.Report(diag::err_drv_invalid_value)