diff --git a/clang/lib/Format/BreakableToken.cpp b/clang/lib/Format/BreakableToken.cpp
--- a/clang/lib/Format/BreakableToken.cpp
+++ b/clang/lib/Format/BreakableToken.cpp
@@ -776,7 +776,7 @@
       // We need to trim the blanks in case this is not the first line in a
       // multiline comment. Then the indent is included in Lines[i].
       StringRef IndentPrefix =
-          getLineCommentIndentPrefix(Lines[i].ltrim(Blanks), Style);
+          getLineCommentIndentPrefix(Lines[i], Style);
       assert((TokenText.startswith("//") || TokenText.startswith("#")) &&
              "unsupported line comment prefix, '//' and '#' are supported");
       OriginalPrefix[i] = Prefix[i] = IndentPrefix;