diff --git a/lib/Frontend/TextDiagnostic.cpp b/lib/Frontend/TextDiagnostic.cpp
index 3c35ab24f2..66362381df 100644
--- a/lib/Frontend/TextDiagnostic.cpp
+++ b/lib/Frontend/TextDiagnostic.cpp
@@ -839,10 +839,13 @@ void TextDiagnostic::emitSnippetAndCaret(
 
   // Get information about the buffer it points into.
   bool Invalid = false;
-  const char *BufStart = SM.getBufferData(FID, &Invalid).data();
+  StringRef BufData = SM.getBufferData(FID, &Invalid);
   if (Invalid)
     return;
 
+  const char *BufStart = BufData.data();
+  const char *BufEnd = BufStart + BufData.size();
+
   unsigned LineNo = SM.getLineNumber(FID, FileOffset);
   unsigned ColNo = SM.getColumnNumber(FID, FileOffset);
   unsigned CaretEndColNo
@@ -856,7 +859,7 @@ void TextDiagnostic::emitSnippetAndCaret(
   // Compute the line end.  Scan forward from the error position to the end of
   // the line.
   const char *LineEnd = TokPtr;
-  while (*LineEnd != '\n' && *LineEnd != '\r' && *LineEnd != '\0')
+  while (*LineEnd != '\n' && *LineEnd != '\r' && LineEnd!=BufEnd)
     ++LineEnd;
 
   // FIXME: This shouldn't be necessary, but the CaretEndColNo can extend past
diff --git a/test/Misc/wnull-character.cpp b/test/Misc/wnull-character.cpp
new file mode 100644
index 0000000000..a618da272a
Binary files /dev/null and b/test/Misc/wnull-character.cpp differ