diff --git a/vlib/v/gen/c/assign.v b/vlib/v/gen/c/assign.v
index 94989b7528c0a8..fdff9d5dd7817e 100644
--- a/vlib/v/gen/c/assign.v
+++ b/vlib/v/gen/c/assign.v
@@ -115,9 +115,17 @@ fn (mut g Gen) expr_opt_with_cast(expr ast.Expr, expr_typ ast.Type, ret_typ ast.
 				g.write('_option_ok(&(${styp}[]) {')
 			}
 			if expr is ast.CastExpr && expr_typ.has_flag(.option) {
-				g.write('*((${g.base_type(expr_typ)}*)')
-				g.expr(expr)
-				g.write('.data)')
+				ret_sym := g.table.sym(ret_typ)
+				if ret_sym.kind == .sum_type {
+					exp_sym := g.table.sym(expr_typ)
+					fname := g.get_sumtype_casting_fn(expr_typ, ret_typ)
+					g.call_cfn_for_casting_expr(fname, expr, ret_typ.is_ptr(), ret_sym.cname,
+						expr_typ.is_ptr(), exp_sym.kind == .function, g.styp(expr_typ))
+				} else {
+					g.write('*((${g.base_type(expr_typ)}*)')
+					g.expr(expr)
+					g.write('.data)')
+				}
 			} else {
 				old_inside_opt_or_res := g.inside_opt_or_res
 				g.inside_opt_or_res = false
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 5532782035ae7f..fd3f8156be78b5 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -2585,7 +2585,7 @@ struct SumtypeCastingFn {
 
 fn (mut g Gen) get_sumtype_casting_fn(got_ ast.Type, exp_ ast.Type) string {
 	mut got, exp := got_.idx_type(), exp_.idx_type()
-	i := int(got) | int(u32(exp) << 17) | int(u32(exp_.has_flag(.option)) << 16)
+	i := int(got) | int(u32(exp) << 18) | int(u32(exp_.has_flag(.option)) << 17) | int(u32(got_.has_flag(.option)) << 16)
 	exp_sym := g.table.sym(exp)
 	mut got_sym := g.table.sym(got)
 	cname := if exp == ast.int_type_idx {
diff --git a/vlib/v/tests/options/option_sumtype_option_variant_test.v b/vlib/v/tests/options/option_sumtype_option_variant_test.v
new file mode 100644
index 00000000000000..549bd83b05f6c1
--- /dev/null
+++ b/vlib/v/tests/options/option_sumtype_option_variant_test.v
@@ -0,0 +1,12 @@
+type Any = ?int | string | ?string
+
+fn test_main() {
+	b := ?Any(?string('bar'))
+	assert b?.str() == "Any(Option('bar'))"
+
+	c := ?Any(string('baz'))
+	assert c?.str() == "Any('baz')"
+
+	d := ?Any('baz')
+	assert d?.str() == "Any('baz')"
+}