diff --git a/clang/lib/AST/Mangle.cpp b/clang/lib/AST/Mangle.cpp
--- a/clang/lib/AST/Mangle.cpp
+++ b/clang/lib/AST/Mangle.cpp
@@ -36,11 +36,18 @@
                                 StringRef Outer,
                                 const BlockDecl *BD,
                                 raw_ostream &Out) {
-  unsigned discriminator = Context.getBlockId(BD, true);
-  if (discriminator == 0)
-    Out << "__" << Outer << "_block_invoke";
-  else
-    Out << "__" << Outer << "_block_invoke_" << discriminator+1;
+  SmallString<256> ParamBuff;
+  llvm::raw_svector_ostream ParamTypes(ParamBuff);
+  for (ParmVarDecl *PVD : BD->parameters()) {
+    Context.mangleTypeName(PVD->getType(), ParamTypes);
+  }
+
+  llvm::MD5 Hash;
+  llvm::MD5::MD5Result Result;
+  Hash.update(ParamTypes.str());
+  Hash.final(Result);
+
+  Out << "__" << Outer << "_block_invoke_" << *(unsigned short*)&Result;
 }
 
 void MangleContext::anchor() { }