diff --git a/common/hsm_version.h b/common/hsm_version.h
index 38a54d7b3..6407f262f 100644
--- a/common/hsm_version.h
+++ b/common/hsm_version.h
@@ -10,7 +10,8 @@
  * v2: dd89bf9323dff42200003fb864abb6608f3aa645b636fdae3ec81d804ac05196
  * v3: edd3d288fc88a5470adc2f99abcbfe4d4af29fae0c7a80b4226f28810a815524
  * v3 without v1: 3f813898f7de490e9126ab817e1c9a29af79c0413d5e37068acedce3ea7b5429
+ * v4: 41a730986c51b930e2d8d12b3169d24966c2004e08d424bdda310edbbde5ba70
  */
 #define HSM_MIN_VERSION 3
-#define HSM_MAX_VERSION 3
+#define HSM_MAX_VERSION 4
 #endif /* LIGHTNING_COMMON_HSM_VERSION_H */
diff --git a/hsmd/hsmd.c b/hsmd/hsmd.c
index 833725599..f4459f3f6 100644
--- a/hsmd/hsmd.c
+++ b/hsmd/hsmd.c
@@ -695,6 +695,7 @@ static struct io_plan *handle_client(struct io_conn *conn, struct client *c)
 	case WIRE_HSMD_SIGN_WITHDRAWAL_REPLY:
 	case WIRE_HSMD_SIGN_INVOICE_REPLY:
 	case WIRE_HSMD_INIT_REPLY_V2:
+	case WIRE_HSMD_INIT_REPLY_V4:
 	case WIRE_HSMD_DERIVE_SECRET_REPLY:
 	case WIRE_HSMSTATUS_CLIENT_BAD_REQUEST:
 	case WIRE_HSMD_SIGN_COMMITMENT_TX_REPLY:
diff --git a/hsmd/hsmd_wire.csv b/hsmd/hsmd_wire.csv
index 05a5bc6a7..ac6fa86e8 100644
--- a/hsmd/hsmd_wire.csv
+++ b/hsmd/hsmd_wire.csv
@@ -19,11 +19,25 @@ msgdata,hsmd_init,hsm_wire_min_version,u32,
 msgdata,hsmd_init,hsm_wire_max_version,u32,
 
 #include <common/bip32.h>
+# DEPRECATED after 23.05, remove in two versions!
 msgtype,hsmd_init_reply_v2,113
 msgdata,hsmd_init_reply_v2,node_id,node_id,
 msgdata,hsmd_init_reply_v2,bip32,ext_key,
 msgdata,hsmd_init_reply_v2,bolt12,pubkey,
 
+# Sorry: I should have put version in v2 :(
+msgtype,hsmd_init_reply_v4,114
+# This gets upgraded when the wire protocol changes in incompatible
+# ways:
+msgdata,hsmd_init_reply_v4,hsm_version,u32,
+# Capabilities, by convention are message numbers, indicating
+# that the HSM supports you sending this message.
+msgdata,hsmd_init_reply_v4,num_hsm_capabilities,u16,
+msgdata,hsmd_init_reply_v4,hsm_capabilities,u32,num_hsm_capabilities
+msgdata,hsmd_init_reply_v4,node_id,node_id,
+msgdata,hsmd_init_reply_v4,bip32,ext_key,
+msgdata,hsmd_init_reply_v4,bolt12,pubkey,
+
 # Declare a new channel.
 msgtype,hsmd_new_channel,30
 msgdata,hsmd_new_channel,id,node_id,
diff --git a/hsmd/libhsmd.c b/hsmd/libhsmd.c
index d04f7e84a..0a362f1b5 100644
--- a/hsmd/libhsmd.c
+++ b/hsmd/libhsmd.c
@@ -137,6 +137,7 @@ bool hsmd_check_client_capabilities(struct hsmd_client *client,
 	case WIRE_HSMD_SIGN_WITHDRAWAL_REPLY:
 	case WIRE_HSMD_SIGN_INVOICE_REPLY:
 	case WIRE_HSMD_INIT_REPLY_V2:
+	case WIRE_HSMD_INIT_REPLY_V4:
 	case WIRE_HSMSTATUS_CLIENT_BAD_REQUEST:
 	case WIRE_HSMD_SIGN_COMMITMENT_TX_REPLY:
 	case WIRE_HSMD_VALIDATE_COMMITMENT_TX_REPLY:
@@ -1662,6 +1663,7 @@ u8 *hsmd_handle_client_message(const tal_t *ctx, struct hsmd_client *client,
 	case WIRE_HSMD_SIGN_WITHDRAWAL_REPLY:
 	case WIRE_HSMD_SIGN_INVOICE_REPLY:
 	case WIRE_HSMD_INIT_REPLY_V2:
+	case WIRE_HSMD_INIT_REPLY_V4:
 	case WIRE_HSMSTATUS_CLIENT_BAD_REQUEST:
 	case WIRE_HSMD_SIGN_COMMITMENT_TX_REPLY:
 	case WIRE_HSMD_VALIDATE_COMMITMENT_TX_REPLY:
@@ -1815,8 +1817,11 @@ u8 *hsmd_init(struct secret hsm_secret,
 
 	/*~ Note: marshalling a bip32 tree only marshals the public side,
 	 * not the secrets!  So we're not actually handing them out here!
+	 *
+	 * And version is 4: we offer limited compatibility (or at least,
+	 * incompatibility detection) with alternate implementations.
 	 */
-	return take(towire_hsmd_init_reply_v2(
-	    NULL, &node_id, &secretstuff.bip32,
-	    &bolt12));
+	return take(towire_hsmd_init_reply_v4(
+			    NULL, 4, NULL, &node_id, &secretstuff.bip32,
+			    &bolt12));
 }
diff --git a/lightningd/hsm_control.c b/lightningd/hsm_control.c
index bdc8a2097..d35dc9453 100644
--- a/lightningd/hsm_control.c
+++ b/lightningd/hsm_control.c
@@ -77,11 +77,23 @@ static unsigned int hsm_msg(struct subd *hsmd,
 	return 0;
 }
 
+/* Is this capability supported by the HSM? (So far, always a message
+ * number) */
+bool hsm_capable(struct lightningd *ld, u32 msgtype)
+{
+	for (size_t i = 0; i < tal_count(ld->hsm_capabilities); i++) {
+		if (ld->hsm_capabilities[i] == msgtype)
+			return true;
+	}
+	return false;
+}
+
 struct ext_key *hsm_init(struct lightningd *ld)
 {
 	u8 *msg;
 	int fds[2];
 	struct ext_key *bip32_base;
+	u32 hsm_version;
 
 	/* We actually send requests synchronously: only status is async. */
 	if (socketpair(AF_LOCAL, SOCK_STREAM, 0, fds) != 0)
@@ -118,14 +130,39 @@ struct ext_key *hsm_init(struct lightningd *ld)
 
 	bip32_base = tal(ld, struct ext_key);
 	msg = wire_sync_read(tmpctx, ld->hsm_fd);
-	if (!fromwire_hsmd_init_reply_v2(msg,
-					 &ld->id, bip32_base,
-					 &ld->bolt12_base)) {
+	if (fromwire_hsmd_init_reply_v4(ld, msg,
+					&hsm_version,
+					&ld->hsm_capabilities,
+					&ld->id, bip32_base,
+					&ld->bolt12_base)) {
+		/* nothing to do. */
+	} else if (fromwire_hsmd_init_reply_v2(msg,
+					       &ld->id, bip32_base,
+					       &ld->bolt12_base)) {
+		/* implicit version */
+		hsm_version = 3;
+		ld->hsm_capabilities = NULL;
+	} else {
 		if (ld->config.keypass)
 			errx(EXITCODE_HSM_BAD_PASSWORD, "Wrong password for encrypted hsm_secret.");
 		errx(EXITCODE_HSM_GENERIC_ERROR, "HSM did not give init reply");
 	}
 
+	if (hsm_version < HSM_MIN_VERSION)
+		errx(EXITCODE_HSM_GENERIC_ERROR,
+		     "HSM version %u below minimum %u",
+		     hsm_version, HSM_MIN_VERSION);
+	if (hsm_version > HSM_MAX_VERSION)
+		errx(EXITCODE_HSM_GENERIC_ERROR,
+		     "HSM version %u above maximum %u",
+		     hsm_version, HSM_MAX_VERSION);
+
+	/* Debugging help */
+	for (size_t i = 0; i < tal_count(ld->hsm_capabilities); i++) {
+		log_debug(ld->hsm->log, "capability +%s",
+			  hsmd_wire_name(ld->hsm_capabilities[i]));
+	}
+
 	/* This is equivalent to makesecret("bolt12-invoice-base") */
 	msg = towire_hsmd_derive_secret(NULL, tal_dup_arr(tmpctx, u8,
 							  (const u8 *)INVOICE_PATH_BASE_STRING,
diff --git a/lightningd/hsm_control.h b/lightningd/hsm_control.h
index e32326c7c..ffef42a81 100644
--- a/lightningd/hsm_control.h
+++ b/lightningd/hsm_control.h
@@ -16,5 +16,9 @@ int hsm_get_client_fd(struct lightningd *ld,
 /* Ask HSM for an fd for a global subdaemon to use (gossipd, connectd) */
 int hsm_get_global_fd(struct lightningd *ld, int capabilities);
 
+/* Is this capability supported by the HSM? (So far, always a message
+ * number) */
+bool hsm_capable(struct lightningd *ld, u32 msgtype);
+
 struct ext_key *hsm_init(struct lightningd *ld);
 #endif /* LIGHTNING_LIGHTNINGD_HSM_CONTROL_H */
diff --git a/lightningd/lightningd.h b/lightningd/lightningd.h
index e0d27b189..2eeaa48ae 100644
--- a/lightningd/lightningd.h
+++ b/lightningd/lightningd.h
@@ -319,6 +319,8 @@ struct lightningd {
 	char *wallet_dsn;
 
 	bool encrypted_hsm;
+	/* What (additional) messages the HSM accepts */
+	u32 *hsm_capabilities;
 
 	mode_t initial_umask;
 
diff --git a/wallet/test/run-wallet.c b/wallet/test/run-wallet.c
index 4f00783fe..a42a8f722 100644
--- a/wallet/test/run-wallet.c
+++ b/wallet/test/run-wallet.c
@@ -1951,6 +1951,7 @@ int main(int argc, const char *argv[])
 
 	ld = tal(tmpctx, struct lightningd);
 	ld->config = test_config;
+	ld->hsm_capabilities = NULL;
 
 	/* Only elements in ld we should access */
 	ld->peers = tal(ld, struct peer_node_id_map);