diff --git a/clang/include/clang/Format/Format.h b/clang/include/clang/Format/Format.h
--- a/clang/include/clang/Format/Format.h
+++ b/clang/include/clang/Format/Format.h
@@ -2617,6 +2617,7 @@
   bool isJson() const { return Language == LK_Json; }
   bool isJavaScript() const { return Language == LK_JavaScript; }
   bool isVerilog() const { return Language == LK_Verilog; }
+  bool isProto() const { return Language == LK_Proto; }
 
   /// Language, this format style is targeted at.
   /// \version 3.5
diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -3097,6 +3097,7 @@
   if (Left.is(tok::semi))
     return 0;
 
+  // Language specific handling.
   if (Style.Language == FormatStyle::LK_Java) {
     if (Right.isOneOf(Keywords.kw_extends, Keywords.kw_throws))
       return 1;
@@ -3116,13 +3117,16 @@
     // Prefer breaking call chains (".foo") over empty "{}", "[]" or "()".
     if (Left.opensScope() && Right.closesScope())
       return 200;
+  } else if (Style.isProto()) {
+    if (Right.is(tok::l_square))
+      return 1;
+    if (Right.is(tok::period))
+      return 500;
   }
 
   if (Right.is(tok::identifier) && Right.Next && Right.Next->is(TT_DictLiteral))
     return 1;
   if (Right.is(tok::l_square)) {
-    if (Style.Language == FormatStyle::LK_Proto)
-      return 1;
     if (Left.is(tok::r_square))
       return 200;
     // Slightly prefer formatting local lambda definitions like functions.
@@ -3135,10 +3139,8 @@
     }
   }
 
-  if (Left.is(tok::coloncolon) ||
-      (Right.is(tok::period) && Style.Language == FormatStyle::LK_Proto)) {
+  if (Left.is(tok::coloncolon))
     return 500;
-  }
   if (Right.isOneOf(TT_StartOfName, TT_FunctionDeclarationName) ||
       Right.is(tok::kw_operator)) {
     if (Line.startsWith(tok::kw_for) && Right.PartOfMultiVariableDeclStmt)