diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index b41fc4419d94f4..21512c87484087 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -654,9 +654,9 @@ and use a reference to the sum type instead: `var := &${node.name}(${variant_nam
 					for typ in sym.info.generic_types {
 						if typ !in node.generic_types {
 							sumtype_type_names := node.generic_types.map(c.table.type_to_str(it)).join(', ')
-							generic_sumtype_name := '${node.name}<${sumtype_type_names}>'
+							generic_sumtype_name := '${node.name}[${sumtype_type_names}]'
 							variant_type_names := sym.info.generic_types.map(c.table.type_to_str(it)).join(', ')
-							generic_variant_name := '${sym.name}<${variant_type_names}>'
+							generic_variant_name := '${sym.name}[${variant_type_names}]'
 							c.error('generic type name `${c.table.sym(typ).name}` of generic struct `${generic_variant_name}` is not mentioned in sumtype `${generic_sumtype_name}`',
 								variant.pos)
 						}
diff --git a/vlib/v/checker/tests/generic_sumtype_decl_err_c.out b/vlib/v/checker/tests/generic_sumtype_decl_err_c.out
index 7e72a7e9f42c11..33adb11405df9f 100644
--- a/vlib/v/checker/tests/generic_sumtype_decl_err_c.out
+++ b/vlib/v/checker/tests/generic_sumtype_decl_err_c.out
@@ -1,7 +1,7 @@
-vlib/v/checker/tests/generic_sumtype_decl_err_c.vv:7:27: error: generic type name `T` of generic struct `Just<T>` is not mentioned in sumtype `Maybe<B>`
+vlib/v/checker/tests/generic_sumtype_decl_err_c.vv:7:27: error: generic type name `T` of generic struct `Just[T]` is not mentioned in sumtype `Maybe[B]`
     5 | struct Nothing {}
-    6 |
+    6 | 
     7 | type Maybe[B] = Nothing | Just[T]
       |                           ~~~~~~~
-    8 |
+    8 | 
     9 | fn main() {