diff --git a/lightningd/closing_control.c b/lightningd/closing_control.c
index 33589e28a..fea6dc864 100644
--- a/lightningd/closing_control.c
+++ b/lightningd/closing_control.c
@@ -55,12 +55,13 @@ static void
 resolve_one_close_command(struct close_command *cc, bool cooperative)
 {
 	struct json_stream *result = json_stream_success(cc->cmd);
-	struct bitcoin_txid txid;
-
-	bitcoin_txid(cc->channel->last_tx, &txid);
 
 	json_add_tx(result, "tx", cc->channel->last_tx);
-	json_add_txid(result, "txid", &txid);
+	if (!invalid_last_tx(cc->channel->last_tx)) {
+		struct bitcoin_txid txid;
+		bitcoin_txid(cc->channel->last_tx, &txid);
+		json_add_txid(result, "txid", &txid);
+	}
 	if (cooperative)
 		json_add_string(result, "type", "mutual");
 	else
diff --git a/lightningd/peer_control.c b/lightningd/peer_control.c
index 0b817c5e5..40bb56812 100644
--- a/lightningd/peer_control.c
+++ b/lightningd/peer_control.c
@@ -220,7 +220,7 @@ static void remove_sig(struct bitcoin_tx *signed_tx)
 	bitcoin_tx_input_set_witness(signed_tx, 0, NULL);
 }
 
-static bool invalid_last_tx(const struct bitcoin_tx *tx)
+bool invalid_last_tx(const struct bitcoin_tx *tx)
 {
 	/* This problem goes back further, but was discovered just before the
 	 * 0.7.1 release. */
diff --git a/lightningd/peer_control.h b/lightningd/peer_control.h
index 3f69729b1..4e9eb5b5d 100644
--- a/lightningd/peer_control.h
+++ b/lightningd/peer_control.h
@@ -121,4 +121,7 @@ command_find_channel(struct command *cmd,
 		     const char *buffer, const jsmntok_t *tok,
 		     struct channel **channel);
 
+/* Ancient (0.7.0 and before) releases could create invalid commitment txs! */
+bool invalid_last_tx(const struct bitcoin_tx *tx);
+
 #endif /* LIGHTNING_LIGHTNINGD_PEER_CONTROL_H */