diff --git a/lightningd/bitcoind.c b/lightningd/bitcoind.c
index 50c7b068e..be2f671d4 100644
--- a/lightningd/bitcoind.c
+++ b/lightningd/bitcoind.c
@@ -787,7 +787,7 @@ void bitcoind_gettxout(struct bitcoind *bitcoind,
  * process the various steps. */
 struct filteredblock_call {
 	struct list_node list;
-	void (*cb)(struct bitcoind *bitcoind, struct filteredblock *fb,
+	void (*cb)(struct bitcoind *bitcoind, const struct filteredblock *fb,
 		   void *arg);
 	void *arg;
 
@@ -914,7 +914,7 @@ process_getfiltered_block_final(struct bitcoind *bitcoind,
 
 void bitcoind_getfilteredblock_(struct bitcoind *bitcoind, u32 height,
 				void (*cb)(struct bitcoind *bitcoind,
-					   struct filteredblock *fb,
+					   const struct filteredblock *fb,
 					   void *arg),
 				void *arg)
 {
diff --git a/lightningd/bitcoind.h b/lightningd/bitcoind.h
index 689d7fed2..cdc43f72b 100644
--- a/lightningd/bitcoind.h
+++ b/lightningd/bitcoind.h
@@ -153,7 +153,7 @@ void bitcoind_getblockhash_(struct bitcoind *bitcoind,
 
 void bitcoind_getfilteredblock_(struct bitcoind *bitcoind, u32 height,
 				void (*cb)(struct bitcoind *bitcoind,
-					   struct filteredblock *fb,
+					   const struct filteredblock *fb,
 					   void *arg),
 				void *arg);
 #define bitcoind_getfilteredblock(bitcoind_, height, cb, arg)		\
diff --git a/lightningd/gossip_control.c b/lightningd/gossip_control.c
index 6001223d2..00a2dee39 100644
--- a/lightningd/gossip_control.c
+++ b/lightningd/gossip_control.c
@@ -60,10 +60,9 @@ static void got_txout(struct bitcoind *bitcoind,
 }
 
 static void got_filteredblock(struct bitcoind *bitcoind,
-		      struct filteredblock *fb,
-		      void *arg)
+		      const struct filteredblock *fb,
+		      struct short_channel_id *scid)
 {
-	struct short_channel_id *scid = (struct short_channel_id *)arg;
 	struct filteredblock_outpoint *fbo = NULL, *o;
 	struct bitcoin_tx_output txo;
 
diff --git a/wallet/wallet.c b/wallet/wallet.c
index 7f09fe774..11c1919d5 100644
--- a/wallet/wallet.c
+++ b/wallet/wallet.c
@@ -2411,7 +2411,7 @@ void wallet_utxoset_add(struct wallet *w, const struct bitcoin_tx *tx,
 	outpointfilter_add(w->utxoset_outpoints, &txid, outnum);
 }
 
-void wallet_filteredblock_add(struct wallet *w, struct filteredblock *fb)
+void wallet_filteredblock_add(struct wallet *w, const struct filteredblock *fb)
 {
 	if (wallet_have_block(w, fb->height))
 		return;
diff --git a/wallet/wallet.h b/wallet/wallet.h
index 09fa42c63..df247e862 100644
--- a/wallet/wallet.h
+++ b/wallet/wallet.h
@@ -1170,6 +1170,6 @@ struct wallet_transaction *wallet_transactions_get(struct wallet *w, const tal_t
  *
  * This can be used to backfill the blocks and still unspent UTXOs that were before our wallet birth height.
  */
-void wallet_filteredblock_add(struct wallet *w, struct filteredblock *fb);
+void wallet_filteredblock_add(struct wallet *w, const struct filteredblock *fb);
 
 #endif /* LIGHTNING_WALLET_WALLET_H */