diff --git a/lib/Format/TokenAnnotator.cpp b/lib/Format/TokenAnnotator.cpp
index 8d08c3d2622734961d0342c2d11f7b9834e05f17..2f1aae39344d65b33f01c59be4bb10f55af06c17 100644
--- a/lib/Format/TokenAnnotator.cpp
+++ b/lib/Format/TokenAnnotator.cpp
@@ -1876,7 +1876,12 @@ bool TokenAnnotator::spaceRequiredBetween(const AnnotatedLine &Line,
 bool TokenAnnotator::spaceRequiredBefore(const AnnotatedLine &Line,
                                          const FormatToken &Right) {
   const FormatToken &Left = *Right.Previous;
-  if (Style.Language == FormatStyle::LK_Proto) {
+  if (Right.Tok.getIdentifierInfo() && Left.Tok.getIdentifierInfo())
+    return true; // Never ever merge two identifiers.
+  if (Style.Language == FormatStyle::LK_Cpp) {
+    if (Left.is(tok::kw_operator))
+      return Right.is(tok::coloncolon);
+  } else if (Style.Language == FormatStyle::LK_Proto) {
     if (Right.is(tok::period) &&
         Left.isOneOf(Keywords.kw_optional, Keywords.kw_required,
                      Keywords.kw_repeated))
@@ -1913,8 +1918,6 @@ bool TokenAnnotator::spaceRequiredBefore(const AnnotatedLine &Line,
         Right.is(TT_TemplateOpener))
       return true;
   }
-  if (Right.Tok.getIdentifierInfo() && Left.Tok.getIdentifierInfo())
-    return true; // Never ever merge two identifiers.
   if (Left.is(TT_ImplicitStringLiteral))
     return Right.WhitespaceRange.getBegin() != Right.WhitespaceRange.getEnd();
   if (Line.Type == LT_ObjCMethodDecl) {
@@ -1937,8 +1940,6 @@ bool TokenAnnotator::spaceRequiredBefore(const AnnotatedLine &Line,
     return false;
   if (Right.isOneOf(TT_CtorInitializerColon, TT_ObjCBlockLParen))
     return true;
-  if (Left.is(tok::kw_operator))
-    return Right.is(tok::coloncolon);
   if (Right.is(TT_OverloadedOperatorLParen))
     return false;
   if (Right.is(tok::colon)) {
diff --git a/unittests/Format/FormatTestProto.cpp b/unittests/Format/FormatTestProto.cpp
index ac8fcbdda4fcf3a36d5f8ca44b4ab981fa75f9ba..74f7005b219fb428e63b43e9ae210c3ed87fe015 100644
--- a/unittests/Format/FormatTestProto.cpp
+++ b/unittests/Format/FormatTestProto.cpp
@@ -63,6 +63,10 @@ TEST_F(FormatTestProto, FormatsMessages) {
                "}");
 }
 
+TEST_F(FormatTestProto, KeywordsInOtherLanguages) {
+  verifyFormat("optional string operator = 1;");
+}
+
 TEST_F(FormatTestProto, FormatsEnums) {
   verifyFormat("enum Type {\n"
                "  UNKNOWN = 0;\n"