diff --git a/doc/changelog.txt b/doc/changelog.txt
index 3a21fb4..91b17d7 100644
--- a/doc/changelog.txt
+++ b/doc/changelog.txt
@@ -1,6 +1,8 @@
 
 HEAD
 ====
+Fixes:
+- xt_pknock: avoid crash when hash TFM could not be allocated
 
 
 v1.33 (2011-02-02)
diff --git a/extensions/pknock/xt_pknock.c b/extensions/pknock/xt_pknock.c
index 4e40911..d7fe379 100644
--- a/extensions/pknock/xt_pknock.c
+++ b/extensions/pknock/xt_pknock.c
@@ -1164,11 +1164,10 @@ static int __init xt_pknock_mt_init(void)
 	}
 
 	crypto.tfm = crypto_alloc_hash(crypto.algo, 0, CRYPTO_ALG_ASYNC);
-
-	if (crypto.tfm == NULL) {
+	if (IS_ERR(crypto.tfm)) {
 		printk(KERN_ERR PKNOCK "failed to load transform for %s\n",
 						crypto.algo);
-		return -ENXIO;
+		return PTR_ERR(crypto.tfm);
 	}
 
 	crypto.size = crypto_hash_digestsize(crypto.tfm);