diff --git a/sql/expression/function/soundex.go b/sql/expression/function/soundex.go
index ed5a99749..fb95dda8c 100644
--- a/sql/expression/function/soundex.go
+++ b/sql/expression/function/soundex.go
@@ -57,7 +57,7 @@ func (s *Soundex) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
 		last = code
 	}
 	if b.Len() == 0 {
-		return "", nil
+		return "0000", nil
 	}
 	for i := len([]rune(b.String())); i < 4; i++ {
 		b.WriteRune('0')
@@ -98,5 +98,5 @@ func (s *Soundex) TransformUp(f sql.TransformExprFunc) (sql.Expression, error) {
 
 // Type implements the Expression interface.
 func (s *Soundex) Type() sql.Type {
-	return s.Child.Type()
+	return sql.Text
 }
diff --git a/sql/expression/function/soundex_test.go b/sql/expression/function/soundex_test.go
index d519c6ffc..32c1b65cc 100644
--- a/sql/expression/function/soundex_test.go
+++ b/sql/expression/function/soundex_test.go
@@ -16,8 +16,8 @@ func TestSoundex(t *testing.T) {
 		expected interface{}
 	}{
 		{"text nil", sql.Text, sql.NewRow(nil), nil},
-		{"text empty", sql.Text, sql.NewRow(""), ""},
-		{"text ignored character", sql.Text, sql.NewRow("-"), ""},
+		{"text empty", sql.Text, sql.NewRow(""), "0000"},
+		{"text ignored character", sql.Text, sql.NewRow("-"), "0000"},
 		{"text runes", sql.Text, sql.NewRow("日本語"), "日000"},
 		{"text Hello ok", sql.Text, sql.NewRow("Hello"), "H400"},
 		{"text Quadratically ok", sql.Text, sql.NewRow("Quadratically"), "Q36324"},
@@ -31,8 +31,9 @@ func TestSoundex(t *testing.T) {
 		{"text Chesley ok", sql.Text, sql.NewRow("Chesley"), "C400"},
 		{"text Tachenion ok", sql.Text, sql.NewRow("Tachenion"), "T250"},
 		{"text Wilcox ok", sql.Text, sql.NewRow("Wilcox"), "W420"},
-		{"binary ok", sql.Blob, sql.NewRow([]byte("Harvey")), "H610"},
-		{"other type", sql.Int32, sql.NewRow(int32(1)), ""},
+		{"binary ok", sql.Text, sql.NewRow([]byte("Harvey")), "H610"},
+		{"string one", sql.Text, sql.NewRow("1"), "0000"},
+		{"other type", sql.Text, sql.NewRow(int32(1)), "0000"},
 	}
 
 	for _, tt := range testCases {