diff --git a/xts/xts.go b/xts/xts.go
index d64f536f9d..65972a181d 100644
--- a/xts/xts.go
+++ b/xts/xts.go
@@ -87,7 +87,7 @@ func (c *Cipher) Encrypt(ciphertext, plaintext []byte, sectorNum uint64) {
 
 	c.k2.Encrypt(tweak[:], tweak[:])
 
-	for len(plaintext) > 0 {
+	for len(plaintext) >= blockSize && len(ciphertext) >= blockSize {
 		for j := range tweak {
 			ciphertext[j] = plaintext[j] ^ tweak[j]
 		}
@@ -126,7 +126,7 @@ func (c *Cipher) Decrypt(plaintext, ciphertext []byte, sectorNum uint64) {
 
 	c.k2.Encrypt(tweak[:], tweak[:])
 
-	for len(ciphertext) > 0 {
+	for len(ciphertext) >= blockSize && len(plaintext) >= blockSize {
 		for j := range tweak {
 			plaintext[j] = ciphertext[j] ^ tweak[j]
 		}
diff --git a/xts/xts_test.go b/xts/xts_test.go
index 75db1c509b..cb6d26e866 100644
--- a/xts/xts_test.go
+++ b/xts/xts_test.go
@@ -106,13 +106,14 @@ func TestShorterCiphertext(t *testing.T) {
 
 func BenchmarkXTS(b *testing.B) {
 	b.ReportAllocs()
+	b.SetBytes(320)
 	c, err := NewCipher(aes.NewCipher, make([]byte, 32))
 	if err != nil {
 		b.Fatalf("NewCipher failed: %s", err)
 	}
-	plaintext := make([]byte, 32)
-	encrypted := make([]byte, 48)
-	decrypted := make([]byte, 48)
+	plaintext := make([]byte, 320)
+	encrypted := make([]byte, 336)
+	decrypted := make([]byte, 336)
 
 	for i := 0; i < b.N; i++ {
 		c.Encrypt(encrypted, plaintext, 0)