diff --git a/src/pki_gcrypt.c b/src/pki_gcrypt.c
index 23572683..870bb0a2 100644
--- a/src/pki_gcrypt.c
+++ b/src/pki_gcrypt.c
@@ -315,7 +315,7 @@ static int privatekey_decrypt(int algo, int mode, unsigned int key_len,
   if (gcry_cipher_open(&cipher, algo, mode, 0)
       || gcry_cipher_setkey(cipher, key, key_len)
       || gcry_cipher_setiv(cipher, iv, iv_len)
-      || (tmp = calloc(ssh_buffer_get_len(data), sizeof(char))) == NULL
+      || (tmp = calloc(ssh_buffer_get_len(data), sizeof(unsigned char))) == NULL
       || gcry_cipher_decrypt(cipher, tmp, ssh_buffer_get_len(data),
                        ssh_buffer_get(data), ssh_buffer_get_len(data))) {
     gcry_cipher_close(cipher);