diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 864d99f6ef..87e345e0a3 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -2090,12 +2090,11 @@ pub fn (mut c Checker) expr(node ast.Expr) table.Type {
 			expr_type_sym := c.table.get_type_symbol(node.expr_type)
 			type_sym := c.table.get_type_symbol(node.typ)
 			if expr_type_sym.kind == .sum_type {
-				info := expr_type_sym.info as table.SumType
 				if type_sym.kind == .placeholder {
 					// Unknown type used in the right part of `as`
 					c.error('unknown type `$type_sym.name`', node.pos)
 				}
-				if node.typ !in info.variants {
+				if !c.table.sumtype_has_variant(node.expr_type, node.typ) {
 					c.error('cannot cast `$expr_type_sym.name` to `$type_sym.name`', node.pos)
 					// c.error('only $info.variants can be casted to `$typ`', node.pos)
 				}
@@ -2122,16 +2121,27 @@ pub fn (mut c Checker) expr(node ast.Expr) table.Type {
 		}
 		ast.CastExpr {
 			node.expr_type = c.expr(node.expr)
-			sym := c.table.get_type_symbol(node.expr_type)
-			if node.typ == table.string_type && !(sym.kind in [.byte, .byteptr] ||
-				(sym.kind == .array && sym.name == 'array_byte')) {
+			from_type_sym := c.table.get_type_symbol(node.expr_type)
+			to_type_sym := c.table.get_type_symbol(node.typ)
+			if to_type_sym.kind == .sum_type {
+				if node.expr_type in [table.any_int_type, table.any_flt_type] {
+					node.expr_type = c.promote_num(
+						node.expr_type,
+						if node.expr_type == table.any_int_type { table.int_type } else { table.f64_type },
+					)
+				}
+				if !c.table.sumtype_has_variant(node.typ, node.expr_type) {
+					c.error('cannot cast `$from_type_sym.name` to `$to_type_sym.name`', node.pos)
+				}
+			}
+			else if node.typ == table.string_type && !(from_type_sym.kind in [.byte, .byteptr] ||
+				(from_type_sym.kind == .array && from_type_sym.name == 'array_byte')) {
 				type_name := c.table.type_to_str(node.expr_type)
 				c.error('cannot cast type `$type_name` to string, use `x.str()` instead',
 					node.pos)
 			}
-			if node.expr_type == table.string_type {
-				cast_to_type_sym := c.table.get_type_symbol(node.typ)
-				if cast_to_type_sym.kind !in [.alias, .sum_type] {
+			else if node.expr_type == table.string_type {
+				if to_type_sym.kind !in [.alias] {
 					mut error_msg := 'cannot cast a string'
 					if node.expr is ast.StringLiteral {
 						str_lit := node.expr as ast.StringLiteral
diff --git a/vlib/v/tests/sum_type_test.v b/vlib/v/tests/sum_type_test.v
index be0b1e8bb6..722985ce30 100644
--- a/vlib/v/tests/sum_type_test.v
+++ b/vlib/v/tests/sum_type_test.v
@@ -133,11 +133,20 @@ type Abc = int | string
 
 fn test_string_cast_to_sumtype() {
 	a := Abc('test')
+	b := Abc(111)
 	match a {
+		int {
+			assert false
+		}
 		string {
 			assert true
 		}
+	}
+	match b {
 		int {
+			assert true
+		}
+		string {
 			assert false
 		}
 	}