Index: lib/Demangle/Demangle.cpp
===================================================================
--- lib/Demangle/Demangle.cpp
+++ lib/Demangle/Demangle.cpp
@@ -15,7 +15,8 @@
 
 std::string llvm::demangle(const std::string &MangledName) {
   char *Demangled;
-  if (MangledName.compare(0, 2, "_Z") == 0)
+  if (MangledName.compare(0, 2, "_Z") == 0 ||
+      MangledName.compare(0, 4, "___Z") == 0)
     Demangled = itaniumDemangle(MangledName.c_str(), nullptr, nullptr, nullptr);
   else
     Demangled =
Index: unittests/Demangle/DemangleTest.cpp
===================================================================
--- unittests/Demangle/DemangleTest.cpp
+++ unittests/Demangle/DemangleTest.cpp
@@ -14,6 +14,8 @@
 
 TEST(Demangle, demangleTest) {
   EXPECT_EQ(demangle("_Z3fooi"), "foo(int)");
+  EXPECT_EQ(demangle("___Z3fooi_block_invoke"),
+            "invocation function for block in foo(int)");
   EXPECT_EQ(demangle("?foo@@YAXH@Z"), "void __cdecl foo(int)");
   EXPECT_EQ(demangle("foo"), "foo");
 }