diff --git a/src/doc/grammar.md b/src/doc/grammar.md
index 690d44cc2cb7b..4bf14c5b51d5f 100644
--- a/src/doc/grammar.md
+++ b/src/doc/grammar.md
@@ -512,7 +512,7 @@ unit_expr : "()" ;
 ```antlr
 struct_expr : expr_path '{' ident ':' expr
                       [ ',' ident ':' expr ] *
-                      [ ".." expr ] '}' |
+                      [ ".." expr ] ? '}' |
               expr_path '(' expr
                       [ ',' expr ] * ')' |
               expr_path ;