diff --git a/src/Init/Lean/Parser/Parser.lean b/src/Init/Lean/Parser/Parser.lean
index f9b269ec91..bea55d2dd4 100644
--- a/src/Init/Lean/Parser/Parser.lean
+++ b/src/Init/Lean/Parser/Parser.lean
@@ -1100,6 +1100,7 @@ fun _ c s =>
 def quotedSymbolFn {k : ParserKind} : ParserFn k :=
 nodeFn `quotedSymbol (andthenFn (andthenFn (chFn '`') (rawFn (fun _ => takeUntilFn (fun c => c == '`')))) (chFn '`' true))
 
+-- TODO: remove after old frontend is gone
 def quotedSymbol {k : ParserKind} : Parser k :=
 { fn := quotedSymbolFn }
 
diff --git a/src/Init/Lean/Parser/Syntax.lean b/src/Init/Lean/Parser/Syntax.lean
index cf9a50ffa4..88f628537b 100644
--- a/src/Init/Lean/Parser/Syntax.lean
+++ b/src/Init/Lean/Parser/Syntax.lean
@@ -54,11 +54,13 @@ def mixfixKind := «prefix» <|> «infix» <|> «infixl» <|> «infixr» <|> «p
 -- TODO delete reserve
 @[builtinCommandParser] def «reserve»  := parser! "reserve " >> mixfixKind >> quotedSymbolPrec
 def mixfixSymbol := quotedSymbolPrec <|> unquotedSymbol
-@[builtinCommandParser] def «mixfix»   := parser! mixfixKind >> mixfixSymbol >> darrow >> termParser
+-- TODO: remove " := " after old frontend is gone
+@[builtinCommandParser] def «mixfix»   := parser! mixfixKind >> mixfixSymbol >> (" := " <|> darrow) >> termParser
 def strLitPrec := parser! strLit >> optPrecedence
 def identPrec  := parser! ident >> optPrecedence
 
-@[builtinCommandParser] def «notation»    := parser! "notation" >> many (strLitPrec <|> quotedSymbolPrec <|> identPrec) >> darrow >> termParser
+-- TODO: remove " := " after old frontend is gone
+@[builtinCommandParser] def «notation»    := parser! "notation" >> many (strLitPrec <|> quotedSymbolPrec <|> identPrec) >> (" := " <|> darrow) >> termParser
 @[builtinCommandParser] def «macro_rules» := parser! "macro_rules" >> many1Indent Term.matchAlt "'match' alternatives must be indented"
 @[builtinCommandParser] def «syntax»      := parser! "syntax " >> optional ("[" >> ident >> "]") >> many1 syntaxParser >> " : " >> ident
 @[builtinCommandParser] def syntaxCat     := parser! "declare_syntax_cat " >> ident