diff --git a/lib/Sema/IdentifierResolver.cpp b/lib/Sema/IdentifierResolver.cpp
index 4441503..027beed 100644
--- a/lib/Sema/IdentifierResolver.cpp
+++ b/lib/Sema/IdentifierResolver.cpp
@@ -151,6 +151,10 @@
     if (S->isDeclScope(D))
       return true;
     if (LangOpt.CPlusPlus) {
+      // C++ 3.3.2p3:
+      // The name declared in a catch exception-declaration is local to the
+      // handler and shall not be redeclared in the outermost block of the
+      // handler.
       // C++ 3.3.2p4:
       // Names declared in the for-init-statement, and in the condition of if,
       // while, for, and switch statements are local to the if, while, for, or