diff --git a/ccan/README b/ccan/README
index ad8207e97..416fbcc12 100644
--- a/ccan/README
+++ b/ccan/README
@@ -1,3 +1,3 @@
 CCAN imported from http://ccodearchive.net.
 
-CCAN version: init-2382-g3ffb94e9
+CCAN version: init-2388-ge6abb93d
diff --git a/ccan/ccan/crypto/shachain/shachain.c b/ccan/ccan/crypto/shachain/shachain.c
index 2c9cb3d54..9cb54a37b 100644
--- a/ccan/ccan/crypto/shachain/shachain.c
+++ b/ccan/ccan/crypto/shachain/shachain.c
@@ -10,7 +10,7 @@ static void change_bit(unsigned char *arr, size_t index)
 	arr[index / CHAR_BIT] ^= (1 << (index % CHAR_BIT));
 }
 
-static unsigned int count_trailing_zeroes(shachain_index_t index)
+static unsigned int count_trailing_zeroes(uint64_t index)
 {
 #if HAVE_BUILTIN_CTZLL
 	return index ? (unsigned int)__builtin_ctzll(index) : SHACHAIN_BITS;
@@ -25,24 +25,24 @@ static unsigned int count_trailing_zeroes(shachain_index_t index)
 #endif
 }
 
-static bool can_derive(shachain_index_t from, shachain_index_t to)
+static bool can_derive(uint64_t from, uint64_t to)
 {
-	shachain_index_t mask;
+	uint64_t mask;
 
 	/* Corner case: can always derive from seed. */
 	if (from == 0)
 		return true;
 
 	/* Leading bits must be the same */
-	mask = ~((1ULL << count_trailing_zeroes(from))-1);
+	mask = ~(((uint64_t)1 << count_trailing_zeroes(from))-1);
 	return ((from ^ to) & mask) == 0;
 }
 
-static void derive(shachain_index_t from, shachain_index_t to,
+static void derive(uint64_t from, uint64_t to,
 		   const struct sha256 *from_hash,
 		   struct sha256 *hash)
 {
-	shachain_index_t branches;
+	uint64_t branches;
 	int i;
 
 	assert(can_derive(from, to));
@@ -60,27 +60,31 @@ static void derive(shachain_index_t from, shachain_index_t to,
 	}
 }
 
-void shachain_from_seed(const struct sha256 *seed, shachain_index_t index,
+void shachain_from_seed(const struct sha256 *seed, uint64_t index,
 			struct sha256 *hash)
 {
 	derive(0, index, seed, hash);
 }
 
+uint64_t shachain_next_index(const struct shachain *chain)
+{
+	return chain->min_index - 1;
+}
+
 void shachain_init(struct shachain *chain)
 {
 	chain->num_valid = 0;
-	chain->min_index = 0;
+	/* This is 0 in the case where SHACHAIN_BITS is 64. */
+	chain->min_index = (UINT64_MAX >> (64 - SHACHAIN_BITS)) + 1;
 }
 
 bool shachain_add_hash(struct shachain *chain,
-		       shachain_index_t index, const struct sha256 *hash)
+		       uint64_t index, const struct sha256 *hash)
 {
 	unsigned int i, pos;
 
 	/* You have to insert them in order! */
-	assert(index == chain->min_index - 1 ||
-	       (index == (shachain_index_t)(UINT64_MAX >> (64 - SHACHAIN_BITS))
-		&& chain->num_valid == 0));
+	assert(index == shachain_next_index(chain));
 
 	pos = count_trailing_zeroes(index);
 
@@ -104,7 +108,7 @@ bool shachain_add_hash(struct shachain *chain,
 }
 
 bool shachain_get_hash(const struct shachain *chain,
-		       shachain_index_t index, struct sha256 *hash)
+		       uint64_t index, struct sha256 *hash)
 {
 	unsigned int i;
 
diff --git a/ccan/ccan/crypto/shachain/shachain.h b/ccan/ccan/crypto/shachain/shachain.h
index 90f2380ed..d95b97363 100644
--- a/ccan/ccan/crypto/shachain/shachain.h
+++ b/ccan/ccan/crypto/shachain/shachain.h
@@ -6,13 +6,8 @@
 #include <stdbool.h>
 #include <stdint.h>
 
-/* Useful for testing. */
-#ifndef shachain_index_t
-#define shachain_index_t uint64_t
-#endif
-
 #ifndef SHACHAIN_BITS
-#define SHACHAIN_BITS (sizeof(shachain_index_t) * 8)
+#define SHACHAIN_BITS (sizeof(uint64_t) * 8)
 #endif
 
 /**
@@ -42,7 +37,7 @@
  *	shachain_from_seed(&seed, index--, hash);
  * }
  */
-void shachain_from_seed(const struct sha256 *seed, shachain_index_t index,
+void shachain_from_seed(const struct sha256 *seed, uint64_t index,
 			struct sha256 *hash);
 
 /**
@@ -55,10 +50,10 @@ void shachain_from_seed(const struct sha256 *seed, shachain_index_t index,
  * added.
  */
 struct shachain {
-	shachain_index_t min_index;
+	uint64_t min_index;
 	unsigned int num_valid;
 	struct {
-		shachain_index_t index;
+		uint64_t index;
 		struct sha256 hash;
 	} known[SHACHAIN_BITS + 1];
 };
@@ -71,20 +66,28 @@ struct shachain {
  */
 void shachain_init(struct shachain *chain);
 
+/**
+ * shachain_next_index - what's the next index I can add to the shachain?
+ * @chain: the chain
+ *
+ * This returns 0xFFFFFFFFFFFFFFFF (for a freshly
+ * initialized chain), or one less than the previously successfully
+ * added value.
+ */
+uint64_t shachain_next_index(const struct shachain *chain);
+
 /**
  * shachain_add_hash - record the hash for the next index.
  * @chain: the chain to add to
  * @index: the index of the hash
  * @hash: the hash value.
  *
- * You can only add index 0xFFFFFFFFFFFFFFFF (for a freshly
- * initialized chain), or one less than the previously successfully
- * added value.
+ * You can only add shachain_next_index(@chain).
  *
  * This can fail (return false without altering @chain) if the hash
  * for this index isn't consistent with previous hashes (ie. wasn't
  * generated from the same seed), though it can't always detect that.
- * If the hash is inconsistent yet undetected, the next addition will
+ * If the hash is inconsistent yet undetected, a future addition will
  * fail.
  *
  * Example:
@@ -98,7 +101,7 @@ void shachain_init(struct shachain *chain);
  * }
  */
 bool shachain_add_hash(struct shachain *chain,
-		       shachain_index_t index, const struct sha256 *hash);
+		       uint64_t index, const struct sha256 *hash);
 
 /**
  * shachain_get_hash - get the hash for a given index.
@@ -129,5 +132,5 @@ bool shachain_add_hash(struct shachain *chain,
  * }
  */
 bool shachain_get_hash(const struct shachain *chain,
-		       shachain_index_t index, struct sha256 *hash);
+		       uint64_t index, struct sha256 *hash);
 #endif /* CCAN_CRYPTO_SHACHAIN_H */
diff --git a/ccan/ccan/crypto/shachain/test/run-8bit.c b/ccan/ccan/crypto/shachain/test/run-8bit.c
index 90b7ef6ce..6fe874bed 100644
--- a/ccan/ccan/crypto/shachain/test/run-8bit.c
+++ b/ccan/ccan/crypto/shachain/test/run-8bit.c
@@ -1,4 +1,4 @@
-#define shachain_index_t uint8_t
+#define SHACHAIN_BITS 8
 
 #include <ccan/crypto/shachain/shachain.h>
 /* Include the C files directly. */
diff --git a/ccan/ccan/crypto/shachain/test/run-can_derive.c b/ccan/ccan/crypto/shachain/test/run-can_derive.c
index 5a1bf4779..693a91a3c 100644
--- a/ccan/ccan/crypto/shachain/test/run-can_derive.c
+++ b/ccan/ccan/crypto/shachain/test/run-can_derive.c
@@ -7,13 +7,13 @@
 
 #include <stdio.h>
 
-static bool bit_set(shachain_index_t index, int bit)
+static bool bit_set(uint64_t index, int bit)
 {
 	return index & (1ULL << bit);
 }
 
 /* As per design.txt */
-static bool naive_can_derive(shachain_index_t from, shachain_index_t to)
+static bool naive_can_derive(uint64_t from, shachain_index_t to)
 {
 	int i;
 
diff --git a/ccan/ccan/crypto/shachain/test/run.c b/ccan/ccan/crypto/shachain/test/run.c
index 36dfaaeb7..c7b4035a2 100644
--- a/ccan/ccan/crypto/shachain/test/run.c
+++ b/ccan/ccan/crypto/shachain/test/run.c
@@ -13,7 +13,7 @@ int main(void)
 	uint64_t i, j;
 
 	/* This is how many tests you plan to run */
-	plan_tests(NUM_TESTS * 3 + NUM_TESTS * (NUM_TESTS + 1) - 1);
+	plan_tests(NUM_TESTS * 4 + NUM_TESTS * (NUM_TESTS + 1) - 1);
 
 	memset(&seed, 0, sizeof(seed));
 	/* Generate a whole heap. */
@@ -34,6 +34,7 @@ int main(void)
 	     i--) {
 		struct sha256 hash;
 		int expidx = 0xFFFFFFFFFFFFFFFFULL - i;
+		ok1(shachain_next_index(&chain) == i);
 		ok1(shachain_add_hash(&chain, i, &expect[expidx]));
 		for (j = i; j != 0; j++) {
 			ok1(shachain_get_hash(&chain, j, &hash));
diff --git a/wallet/wallet.c b/wallet/wallet.c
index 54252d520..672def1da 100644
--- a/wallet/wallet.c
+++ b/wallet/wallet.c
@@ -252,7 +252,7 @@ bool wallet_shachain_init(struct wallet *wallet, struct wallet_shachain *chain)
 }
 
 /* TODO(cdecker) Stolen from shachain, move to some appropriate location */
-static unsigned int count_trailing_zeroes(shachain_index_t index)
+static unsigned int count_trailing_zeroes(uint64_t index)
 {
 #if HAVE_BUILTIN_CTZLL
 	return index ? (unsigned int)__builtin_ctzll(index) : SHACHAIN_BITS;
@@ -269,7 +269,7 @@ static unsigned int count_trailing_zeroes(shachain_index_t index)
 
 bool wallet_shachain_add_hash(struct wallet *wallet,
 			      struct wallet_shachain *chain,
-			      shachain_index_t index,
+			      uint64_t index,
 			      const struct sha256 *hash)
 {
 	tal_t *tmpctx = tal_tmpctx(wallet);
diff --git a/wallet/wallet.h b/wallet/wallet.h
index 00db5745a..2b0e110f3 100644
--- a/wallet/wallet.h
+++ b/wallet/wallet.h
@@ -142,7 +142,7 @@ bool wallet_shachain_init(struct wallet *wallet, struct wallet_shachain *chain);
  */
 bool wallet_shachain_add_hash(struct wallet *wallet,
 			      struct wallet_shachain *chain,
-			      shachain_index_t index,
+			      uint64_t index,
 			      const struct sha256 *hash);
 
 /* Simply passes through to shachain_get_hash since it doesn't touch
diff --git a/wallet/wallet_tests.c b/wallet/wallet_tests.c
index 9c29623b4..387271327 100644
--- a/wallet/wallet_tests.c
+++ b/wallet/wallet_tests.c
@@ -81,7 +81,7 @@ static bool test_shachain_crud(void)
 	int fd = mkstemp(filename);
 	struct wallet *w = tal(NULL, struct wallet);
 	struct sha256 seed, hash;
-	shachain_index_t index = UINT64_MAX >> (64 - SHACHAIN_BITS);
+	uint64_t index = UINT64_MAX >> (64 - SHACHAIN_BITS);
 
 	w->db = db_open(w, filename);
 	CHECK_MSG(w->db, "Failed opening the db");
@@ -99,7 +99,8 @@ static bool test_shachain_crud(void)
 
 	CHECK(a.id == 1);
 
-	CHECK(a.chain.num_valid == 0 && a.chain.min_index == 0);
+	CHECK(a.chain.num_valid == 0);
+	CHECK(shachain_next_index(&a.chain) == index);
 
 	for (int i=0; i<100; i++) {
 		shachain_from_seed(&seed, index, &hash);