Index: include/llvm/ADT/StringRef.h
===================================================================
--- include/llvm/ADT/StringRef.h
+++ include/llvm/ADT/StringRef.h
@@ -73,14 +73,9 @@
     /// Construct an empty string ref.
     /*implicit*/ StringRef() : Data(nullptr), Length(0) {}
 
-    StringRef(std::nullptr_t) = delete;
-
     /// Construct a string ref from a cstring.
     /*implicit*/ StringRef(const char *Str)
-      : Data(Str) {
-        assert(Str && "StringRef cannot be built from a NULL argument");
-        Length = ::strlen(Str); // invoking strlen(NULL) is undefined behavior
-      }
+        : Data(Str), Length(Str ? ::strlen(Str) : 0) {}
 
     /// Construct a string ref from a pointer and length.
     LLVM_ATTRIBUTE_ALWAYS_INLINE