diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index d04426c71a..00e41a393f 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1749,7 +1749,9 @@ fn (mut c Checker) stmts(stmts []ast.Stmt) {
 
 pub fn (mut c Checker) unwrap_generic(typ table.Type) table.Type {
 	if typ.idx() == table.t_type_idx {
-		return c.cur_generic_type
+		// return c.cur_generic_type
+		// its more efficient to set the id rather than to copy flags/nr_muls
+		return typ.set_idx(c.cur_generic_type)
 	}
 	return typ
 }
diff --git a/vlib/v/gen/fn.v b/vlib/v/gen/fn.v
index 051b76dd22..6f97481ad2 100644
--- a/vlib/v/gen/fn.v
+++ b/vlib/v/gen/fn.v
@@ -243,7 +243,7 @@ fn (mut g Gen) fn_args(args []table.Arg, is_variadic bool) ([]string, []string)
 	no_names := args.len > 0 && args[0].name == 'arg_1'
 	for i, arg in args {
 		caname := c_name(arg.name)
-		typ := g.unwrap_generic(arg.typ).set_nr_muls(arg.typ.nr_muls())
+		typ := g.unwrap_generic(arg.typ)
 		arg_type_sym := g.table.get_type_symbol(typ)
 		mut arg_type_name := g.typ(typ) // arg_type_sym.name.replace('.', '__')
 		// if arg.name == 'xxx' {
@@ -330,7 +330,9 @@ fn (mut g Gen) call_expr(node ast.CallExpr) {
 
 pub fn (mut g Gen) unwrap_generic(typ table.Type) table.Type {
 	if typ.idx() == table.t_type_idx {
-		return g.cur_generic_type
+		// return g.cur_generic_type
+		// its more efficient to set the id rather than to copy flags/nr_muls
+		return typ.set_idx(g.cur_generic_type)
 	}
 	return typ
 }
diff --git a/vlib/v/table/atypes.v b/vlib/v/table/atypes.v
index df14032f48..bbaa8c3f48 100644
--- a/vlib/v/table/atypes.v
+++ b/vlib/v/table/atypes.v
@@ -70,6 +70,12 @@ pub fn (t Type) is_ptr() bool {
 	return (int(t) >> 16) & 0xff > 0
 }
 
+// set idx on `t` and return it
+[inline]
+pub fn (t Type) set_idx(idx int) Type {
+	return (((int(t) >> 24) & 0xff) << 24) | (((int(t) >> 16) & 0xff) << 16) | (u16(idx) & 0xffff)
+}
+
 // set nr_muls on `t` and return it
 [inline]
 pub fn (t Type) set_nr_muls(nr_muls int) Type {
@@ -112,11 +118,12 @@ pub fn (t Type) clear_flag(flag TypeFlag) Type {
 }
 
 // clear all flags
+[inline]
 pub fn (t Type) clear_flags() Type {
 	return 0 | (((int(t) >> 16) & 0xff) << 16) | (u16(t) & 0xffff)
 }
 
-// return true if `flag` is set in `t`
+// return true if `flag` is set on `t`
 [inline]
 pub fn (t Type) has_flag(flag TypeFlag) bool {
 	return (((int(t) >> 24) & 0xff) >> int(flag)) & 1 == 1