diff --git a/crypto/chachapoly.c b/crypto/chachapoly.c
--- a/crypto/chachapoly.c
+++ b/crypto/chachapoly.c
@@ -73,6 +73,7 @@
 
 	/* Initialize the authenticator. */
 	poly1305_init(&ctx->poly, poly_key);
+	explicit_bzero(poly_key, sizeof(poly_key));
 
 	ctx->flags |= (enc_mode ? F_MODE_ENCRYPTION : 0);
 	ctx->flags |= F_INITIALIZED;