diff --git a/lib/Bitcode/Reader/BitcodeReader.cpp b/lib/Bitcode/Reader/BitcodeReader.cpp
index b3f0776..f486b51 100644
--- a/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -39,6 +39,7 @@
   std::vector<BasicBlock*>().swap(FunctionBBs);
   std::vector<Function*>().swap(FunctionsWithBodies);
   DeferredFunctionInfo.clear();
+  MDKindMap.clear();
 }
 
 //===----------------------------------------------------------------------===//
@@ -859,13 +860,12 @@
       SmallString<8> Name;
       Name.resize(RecordLength-1);
       unsigned Kind = Record[0];
-      (void) Kind;
       for (unsigned i = 1; i != RecordLength; ++i)
         Name[i-1] = Record[i];
       
       unsigned NewKind = TheModule->getMDKindID(Name.str());
-      assert(Kind == NewKind &&
-             "FIXME: Unable to handle custom metadata mismatch!");(void)NewKind;
+      if (!MDKindMap.insert(std::make_pair(Kind, NewKind)).second)
+        return Error("Conflicting METADATA_KIND records");
       break;
     }
     }
@@ -1621,8 +1621,12 @@
       Instruction *Inst = InstructionList[Record[0]];
       for (unsigned i = 1; i != RecordLength; i = i+2) {
         unsigned Kind = Record[i];
+        DenseMap<unsigned, unsigned>::iterator I =
+          MDKindMap.find(Kind);
+        if (I == MDKindMap.end())
+          return Error("Invalid metadata kind ID");
         Value *Node = MDValueList.getValueFwdRef(Record[i+1]);
-        Inst->setMetadata(Kind, cast<MDNode>(Node));
+        Inst->setMetadata(I->second, cast<MDNode>(Node));
       }
       break;
     }
diff --git a/lib/Bitcode/Reader/BitcodeReader.h b/lib/Bitcode/Reader/BitcodeReader.h
index 55c71f7..a5ab5d2 100644
--- a/lib/Bitcode/Reader/BitcodeReader.h
+++ b/lib/Bitcode/Reader/BitcodeReader.h
@@ -156,6 +156,9 @@
   // stored here with their replacement function.
   typedef std::vector<std::pair<Function*, Function*> > UpgradedIntrinsicMap;
   UpgradedIntrinsicMap UpgradedIntrinsics;
+
+  // Map the bitcode's custom MDKind ID to the Module's MDKind ID.
+  DenseMap<unsigned, unsigned> MDKindMap;
   
   // After the module header has been read, the FunctionsWithBodies list is 
   // reversed.  This keeps track of whether we've done this yet.
diff --git a/lib/Bitcode/Writer/BitcodeWriter.cpp b/lib/Bitcode/Writer/BitcodeWriter.cpp
index fa1b2c4..985c16c 100644
--- a/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -634,12 +634,11 @@
   SmallVector<StringRef, 4> Names;
   M->getMDKindNames(Names);
   
-  assert(Names[0] == "" && "MDKind #0 is invalid");
-  if (Names.size() == 1) return;
+  if (Names.empty()) return;
 
   Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
   
-  for (unsigned MDKindID = 1, e = Names.size(); MDKindID != e; ++MDKindID) {
+  for (unsigned MDKindID = 0, e = Names.size(); MDKindID != e; ++MDKindID) {
     Record.push_back(MDKindID);
     StringRef KName = Names[MDKindID];
     Record.append(KName.begin(), KName.end());
diff --git a/lib/VMCore/LLVMContext.cpp b/lib/VMCore/LLVMContext.cpp
index 4d61363..563c651 100644
--- a/lib/VMCore/LLVMContext.cpp
+++ b/lib/VMCore/LLVMContext.cpp
@@ -110,21 +110,18 @@
 /// getMDKindID - Return a unique non-zero ID for the specified metadata kind.
 unsigned LLVMContext::getMDKindID(StringRef Name) const {
   assert(isValidName(Name) && "Invalid MDNode name");
-  
-  unsigned &Entry = pImpl->CustomMDKindNames[Name];
-  
+
   // If this is new, assign it its ID.
-  if (Entry == 0) Entry = pImpl->CustomMDKindNames.size();
-  return Entry;
+  return
+    pImpl->CustomMDKindNames.GetOrCreateValue(
+      Name, pImpl->CustomMDKindNames.size()).second;
 }
 
 /// getHandlerNames - Populate client supplied smallvector using custome
 /// metadata name and ID.
 void LLVMContext::getMDKindNames(SmallVectorImpl<StringRef> &Names) const {
-  Names.resize(pImpl->CustomMDKindNames.size()+1);
-  Names[0] = "";
+  Names.resize(pImpl->CustomMDKindNames.size());
   for (StringMap<unsigned>::const_iterator I = pImpl->CustomMDKindNames.begin(),
        E = pImpl->CustomMDKindNames.end(); I != E; ++I)
-    // MD Handlers are numbered from 1.
     Names[I->second] = I->first();
 }