diff --git a/crypto/ghash-generic.c b/crypto/ghash-generic.c
index be44256..7835b8f 100644
--- a/crypto/ghash-generic.c
+++ b/crypto/ghash-generic.c
@@ -67,6 +67,9 @@
 	struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
 	u8 *dst = dctx->buffer;
 
+	if (!ctx->gf128)
+		return -ENOKEY;
+
 	if (dctx->bytes) {
 		int n = min(srclen, dctx->bytes);
 		u8 *pos = dst + (GHASH_BLOCK_SIZE - dctx->bytes);
@@ -119,6 +122,9 @@
 	struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
 	u8 *buf = dctx->buffer;
 
+	if (!ctx->gf128)
+		return -ENOKEY;
+
 	ghash_flush(ctx, dctx);
 	memcpy(dst, buf, GHASH_BLOCK_SIZE);