diff --git a/crypto/Kconfig b/crypto/Kconfig
index 0e35889..b582ea7 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -157,6 +157,7 @@
 	  These are 'Null' algorithms, used by IPsec, which do nothing.
 
 config CRYPTO_NULL2
+	tristate
 	select CRYPTO_ALGAPI2
 	select CRYPTO_BLKCIPHER2
 	select CRYPTO_HASH2