diff --git a/lib/MC/MCInstPrinter.cpp b/lib/MC/MCInstPrinter.cpp
index 6a452c8d4a7..ba71245d018 100644
--- a/lib/MC/MCInstPrinter.cpp
+++ b/lib/MC/MCInstPrinter.cpp
@@ -31,9 +31,13 @@ void MCInstPrinter::printRegName(raw_ostream &OS, unsigned RegNo) const {
 
 void MCInstPrinter::printAnnotation(raw_ostream &OS, StringRef Annot) {
   if (!Annot.empty()) {
-    if (CommentStream)
+    if (CommentStream) {
       (*CommentStream) << Annot;
-    else
+      // By definition (see MCInstPrinter.h), CommentStream must end with
+      // a newline after each comment.
+      if (Annot.back() != '\n')
+        (*CommentStream) << '\n';
+    } else
       OS << " " << MAI.getCommentString() << " " << Annot;
   }
 }