bitcoin: have random_scid() function.

diff --git a/bitcoin/short_channel_id.c b/bitcoin/short_channel_id.c
index 80e7d28a..cc1de68c 100644
--- a/bitcoin/short_channel_id.c
+++ b/bitcoin/short_channel_id.c
@@ -1,6 +1,7 @@
 #include "config.h"
 #include <bitcoin/short_channel_id.h>
 #include <ccan/tal/str/str.h>
+#include <sodium/randombytes.h>
 #include <stdio.h>
 #include <wire/wire.h>
 
@@ -99,3 +100,10 @@ struct short_channel_id fromwire_short_channel_id(const u8 **cursor, size_t *max
 	scid.u64 = fromwire_u64(cursor, max);
 	return scid;
 }
+
+struct short_channel_id random_scid(void)
+{
+	struct short_channel_id scid;
+	randombytes_buf(&scid, sizeof(scid));
+	return scid;
+}
diff --git a/bitcoin/short_channel_id.h b/bitcoin/short_channel_id.h
index cf382d69..1cd13f9a 100644
--- a/bitcoin/short_channel_id.h
+++ b/bitcoin/short_channel_id.h
@@ -98,4 +98,6 @@ void towire_short_channel_id(u8 **pptr,
 			     struct short_channel_id short_channel_id);
 struct short_channel_id fromwire_short_channel_id(const u8 **cursor, size_t *max);
 
+/* Set to random bytes */
+struct short_channel_id random_scid(void);
 #endif /* LIGHTNING_BITCOIN_SHORT_CHANNEL_ID_H */
diff --git a/lightningd/channel.c b/lightningd/channel.c
index ff673df1..589860e1 100644
--- a/lightningd/channel.c
+++ b/lightningd/channel.c
@@ -17,7 +17,6 @@
 #include <lightningd/opening_common.h>
 #include <lightningd/peer_control.h>
 #include <lightningd/subd.h>
-#include <sodium/randombytes.h>
 #include <wallet/txfilter.h>
 #include <wire/peer_wire.h>
 
@@ -285,7 +284,7 @@ static void channel_set_random_local_alias(struct channel *channel)
 {
 	assert(channel->alias[LOCAL] == NULL);
 	channel->alias[LOCAL] = tal(channel, struct short_channel_id);
-	randombytes_buf(channel->alias[LOCAL], sizeof(struct short_channel_id));
+	*channel->alias[LOCAL] = random_scid();
 	/* We don't check for uniqueness.  We would crash on a clash, but your machine is
 	 * probably broken beyond repair if it gets two equal 64 bit numbers */
 	chanmap_add(channel->peer->ld, channel, *channel->alias[LOCAL]);
diff --git a/wallet/db.c b/wallet/db.c
index 15c54eb0..bc7b0256 100644
--- a/wallet/db.c
+++ b/wallet/db.c
@@ -2021,13 +2021,11 @@ static void migrate_initialize_alias_local(struct lightningd *ld,
 	tal_free(stmt);
 
 	for (size_t i = 0; i < tal_count(ids); i++) {
-		struct short_channel_id alias;
 		stmt = db_prepare_v2(db, SQL("UPDATE channels"
 					     " SET alias_local = ?"
 					     " WHERE id = ?;"));
 		/* We don't even check for clashes! */
-		randombytes_buf(&alias, sizeof(alias));
-		db_bind_short_channel_id(stmt, alias);
+		db_bind_short_channel_id(stmt, random_scid());
 		db_bind_u64(stmt, ids[i]);
 		db_exec_prepared_v2(stmt);
 		tal_free(stmt);
diff --git a/wallet/test/run-wallet.c b/wallet/test/run-wallet.c
index 6cfe7f83..0e96b9d1 100644
--- a/wallet/test/run-wallet.c
+++ b/wallet/test/run-wallet.c
@@ -1366,6 +1366,9 @@ static struct wallet *create_test_wallet(struct lightningd *ld, const tal_t *ctx
 	CHECK_MSG(!wallet_err, wallet_err);
 	w->max_channel_dbid = 0;
 
+	/* Create fresh channels map */
+	ld->channels_by_scid = tal(ld, struct channel_scid_map);
+	channel_scid_map_init(ld->channels_by_scid);
 	return w;
 }
 
@@ -2092,6 +2095,9 @@ static bool test_channel_inflight_crud(struct lightningd *ld, const tal_t *ctx)
 	/* do inflights get correctly added to the channel? */
 	wallet_inflight_add(w, inflight);
 
+	/* Hack to remove scids from htable so we don't clash! */
+	chanmap_remove(ld, chan, *chan->alias[LOCAL]);
+
 	/* do inflights get correctly loaded from the database? */
 	CHECK_MSG(c2 = wallet_channel_load(w, chan->dbid),
 		  tal_fmt(w, "Load from DB"));