diff --git a/cryptobox/crypto_box_seal.go b/cryptobox/crypto_box_seal.go
index 1ec1677..09c99cf 100644
--- a/cryptobox/crypto_box_seal.go
+++ b/cryptobox/crypto_box_seal.go
@@ -8,7 +8,7 @@ import "github.com/GoKillers/libsodium-go/support"
 
 func CryptoBoxSeal(m []byte, pk []byte) ([]byte, int) {
 	support.CheckSize(pk, CryptoBoxPublicKeyBytes(), "public key")
-	c := make([]byte, len(m)+CryptoBoxMacBytes())
+	c := make([]byte, len(m)+CryptoBoxSealBytes())
 	exit := int(C.crypto_box_seal(
 		(*C.uchar)(&c[0]),
 		(*C.uchar)(&m[0]),
@@ -21,7 +21,7 @@ func CryptoBoxSeal(m []byte, pk []byte) ([]byte, int) {
 func CryptoBoxSealOpen(c []byte, pk []byte, sk []byte) ([]byte, int) {
 	support.CheckSize(pk, CryptoBoxPublicKeyBytes(), "public key")
 	support.CheckSize(sk, CryptoBoxSecretKeyBytes(), "secret key")
-	m := make([]byte, len(c)-CryptoBoxMacBytes())
+	m := make([]byte, len(c)-CryptoBoxSealBytes())
 	exit := int(C.crypto_box_seal_open(
 		(*C.uchar)(&m[0]),
 		(*C.uchar)(&c[0]),
diff --git a/cryptobox/crypto_box_seal_test.go b/cryptobox/crypto_box_seal_test.go
new file mode 100644
index 0000000..5c3a73c
--- /dev/null
+++ b/cryptobox/crypto_box_seal_test.go
@@ -0,0 +1,22 @@
+package cryptobox
+
+import "testing"
+
+func TestCryptoBoxSeal(t *testing.T) {
+	sk, pk, exit := CryptoBoxKeyPair()
+	if exit != 0 {
+		t.Fatalf("CryptoBoxKeyPair failed: %v", exit)
+	}
+	testStr := "test string 12345678901234567890123456789012345678901234567890"
+	cipherText, exit := CryptoBoxSeal([]byte(testStr), pk)
+	if exit != 0 {
+		t.Fatalf("CryptoBoxSeal failed: %v", exit)
+	}
+	plaintext, exit := CryptoBoxSealOpen(cipherText, pk, sk)
+	if exit != 0 {
+		t.Fatalf("CryptoBoxSealOpen failed: %v", exit)
+	}
+	if string(plaintext) != testStr {
+		t.Fatalf("Bad plaintext: %#v", plaintext)
+	}
+}