diff --git a/lib/AsmParser/LLLexer.cpp b/lib/AsmParser/LLLexer.cpp
index 1e6085b443f..3c384f5fcca 100644
--- a/lib/AsmParser/LLLexer.cpp
+++ b/lib/AsmParser/LLLexer.cpp
@@ -275,6 +275,10 @@ lltok::Kind LLLexer::LexAt() {
       if (CurChar == '"') {
         StrVal.assign(TokStart+2, CurPtr-1);
         UnEscapeLexed(StrVal);
+        if (StringRef(StrVal).find_first_of(0) != StringRef::npos) {
+          Error("Null bytes are not allowed in names");
+          return lltok::Error;
+        }
         return lltok::GlobalVar;
       }
     }
diff --git a/lib/IR/Value.cpp b/lib/IR/Value.cpp
index 62a3b31c18b..2c90383edd8 100644
--- a/lib/IR/Value.cpp
+++ b/lib/IR/Value.cpp
@@ -182,6 +182,8 @@ void Value::setName(const Twine &NewName) {
 
   SmallString<256> NameData;
   StringRef NameRef = NewName.toStringRef(NameData);
+  assert(NameRef.find_first_of(0) == StringRef::npos &&
+         "Null bytes are not allowed in names");
 
   // Name isn't changing?
   if (getName() == NameRef)
diff --git a/test/Assembler/invalid-name.ll b/test/Assembler/invalid-name.ll
new file mode 100644
index 00000000000..d9d7a110880
--- /dev/null
+++ b/test/Assembler/invalid-name.ll
@@ -0,0 +1,6 @@
+; RUN: not llvm-as %s 2>&1 | FileCheck %s
+
+; CHECK: expected function name
+define void @"zed\00bar"() {
+  ret void
+}