--- a/cbc_decrypt.c	Mon May 31 18:25:41 2004 +0000
+++ b/cbc_decrypt.c	Tue Jun 15 14:07:21 2004 +0000
@@ -25,14 +25,15 @@
    if ((err = cipher_is_valid(cbc->cipher)) != CRYPT_OK) {
        return err;
    }
-   cipher_descriptor[cbc->cipher].ecb_decrypt(ct, tmp, &cbc->key);
-   
+   _ARGCHK(cipher_descriptor[cbc->cipher].ecb_decrypt != NULL);
+      
    /* is blocklen valid? */
    if (cbc->blocklen < 0 || cbc->blocklen > (int)sizeof(cbc->IV)) {
       return CRYPT_INVALID_ARG;
    } 
 
-   /* xor IV against the plaintext of the previous step */
+   /* decrypt and xor IV against the plaintext of the previous step */
+   cipher_descriptor[cbc->cipher].ecb_decrypt(ct, tmp, &cbc->key);
    for (x = 0; x < cbc->blocklen; x++) { 
        /* copy CT in case ct == pt */
        tmp2[x] = ct[x];