diff --git a/rosidl_parser/rosidl_parser/grammar.lark b/rosidl_parser/rosidl_parser/grammar.lark
index 686a203ee..4a6b1ba82 100644
--- a/rosidl_parser/rosidl_parser/grammar.lark
+++ b/rosidl_parser/rosidl_parser/grammar.lark
@@ -198,7 +198,7 @@ positive_int_const: const_expr
 
 // (20)
 type_dcl: constr_type_dcl
-  | native_dcl
+//  | native_dcl
   | typedef_dcl
 
 // (21), (216)
@@ -304,7 +304,7 @@ fixed_pt_const_type.2: "fixed"
 
 // (44)
 constr_type_dcl: struct_dcl
-  | union_dcl
+//  | union_dcl
   | enum_dcl
 
 // (45)
@@ -321,11 +321,11 @@ member: annotation_appl* type_spec declarators ";"
 struct_forward_dcl: "struct" IDENTIFIER
 
 // (49)
-union_dcl: union_def
-  | union_forward_dcl
+//union_dcl: union_def
+//  | union_forward_dcl
 
 // (50)
-union_def: "union" IDENTIFIER "switch" "(" switch_type_spec ")" "{" switch_body "}"
+//union_def: "union" IDENTIFIER "switch" "(" switch_type_spec ")" "{" switch_body "}"
 
 // (51)
 switch_type_spec: integer_type
@@ -347,7 +347,7 @@ case_label: "case" const_expr ":"
 element_spec: type_spec declarator
 
 // (56)
-union_forward_dcl: "union" IDENTIFIER
+//union_forward_dcl: "union" IDENTIFIER
 
 // (57)
 enum_dcl: annotation_appl* "enum" IDENTIFIER "{" enumerator ("," enumerator)* "}"
@@ -362,7 +362,7 @@ array_declarator: IDENTIFIER fixed_array_size+
 fixed_array_size: "[" positive_int_const "]"
 
 // (61)
-native_dcl: "native" simple_declarator
+//native_dcl: "native" simple_declarator
 
 // (62)
 simple_declarator: IDENTIFIER