diff --git a/shadouble.c b/shadouble.c
index 8135430b5..028ef483d 100644
--- a/shadouble.c
+++ b/shadouble.c
@@ -2,12 +2,12 @@
 
 void sha256_double(struct sha256_double *shadouble, const void *p, size_t len)
 {
-	sha256(&shadouble->sha, (unsigned char *)p, len);
-	sha256(&shadouble->sha, &shadouble->sha, 1);
+	sha256(&shadouble->sha, p, len);
+	sha256(&shadouble->sha, &shadouble->sha, sizeof(shadouble->sha));
 }
 
-void sha256_double_done(struct sha256_ctx *sha256, struct sha256_double *res)
+void sha256_double_done(struct sha256_ctx *shactx, struct sha256_double *res)
 {
-	sha256_done(sha256, &res->sha);
-	sha256(&res->sha, &res->sha, 1);
+	sha256_done(shactx, &res->sha);
+	sha256(&res->sha, &res->sha, sizeof(res->sha));
 }