diff --git a/fs/bcachefs/checksum.c b/fs/bcachefs/checksum.c
index 3bd3aba90d8f..77b29c73d7a0 100644
--- a/fs/bcachefs/checksum.c
+++ b/fs/bcachefs/checksum.c
@@ -220,10 +220,11 @@ struct bch_csum bch2_checksum(struct bch_fs *c, unsigned type,
 
 	case BCH_CSUM_chacha20_poly1305_80:
 	case BCH_CSUM_chacha20_poly1305_128: {
+		struct bch_csum ret = { 0 };
+		if (!c)
+			return ret;
 		SHASH_DESC_ON_STACK(desc, c->poly1305);
 		u8 digest[POLY1305_DIGEST_SIZE];
-		struct bch_csum ret = { 0 };
-
 		gen_poly_key(c, desc, nonce);
 
 		crypto_shash_update(desc, data, len);