diff --git a/clang/lib/Format/BreakableToken.cpp b/clang/lib/Format/BreakableToken.cpp
index db7361bf5f2ff..94bd9823e1f5a 100644
--- a/clang/lib/Format/BreakableToken.cpp
+++ b/clang/lib/Format/BreakableToken.cpp
@@ -785,7 +785,16 @@ BreakableLineCommentSection::BreakableLineCommentSection(
                 Lines[i].substr(IndentPrefix.size(), FirstCharByteSize),
                 Encoding) != 1)
           return false;
-        if (FirstCommentChar == '#')
+        // In C-like comments, add a space before #. For example this is useful
+        // to preserve the relative indentation when commenting out code with
+        // #includes.
+        //
+        // In languages using # as the comment leader such as proto, don't
+        // add a space to support patterns like:
+        // #########
+        // # section
+        // #########
+        if (FirstCommentChar == '#' && !TokenText.startswith("#"))
           return false;
         return FirstCommentChar == '\\' || isPunctuation(FirstCommentChar) ||
                isHorizontalWhitespace(FirstCommentChar);
diff --git a/clang/unittests/Format/FormatTestTextProto.cpp b/clang/unittests/Format/FormatTestTextProto.cpp
index 44b67d275bcc3..10a43c1519d6d 100644
--- a/clang/unittests/Format/FormatTestTextProto.cpp
+++ b/clang/unittests/Format/FormatTestTextProto.cpp
@@ -408,6 +408,23 @@ TEST_F(FormatTestTextProto, UnderstandsHashComments) {
                    "dd: 100\n"
                    "#### another quadriple-hash comment\n",
                    Style));
+
+  // Ensure we support a common pattern for naming sections.
+  EXPECT_EQ("##############\n"
+            "# section name\n"
+            "##############",
+            format("##############\n"
+                   "# section name\n"
+                   "##############",
+                   Style));
+
+  EXPECT_EQ("///////////////\n"
+            "// section name\n"
+            "///////////////",
+            format("///////////////\n"
+                   "// section name\n"
+                   "///////////////",
+                   Style));
 }
 
 TEST_F(FormatTestTextProto, FormatsExtensions) {