diff --git a/lightningd/channel.c b/lightningd/channel.c
index c7201de2fc1a..cd26e229eaff 100644
--- a/lightningd/channel.c
+++ b/lightningd/channel.c
@@ -859,7 +859,7 @@ void channel_set_state(struct channel *channel,
 		       enum channel_state old_state,
 		       enum channel_state state,
 		       enum state_change reason,
-		       char *why)
+		       const char *why)
 {
 	/* set closer, if known */
 	if (channel_state_closing(state) && channel->closer == NUM_SIDES) {
diff --git a/lightningd/channel.h b/lightningd/channel.h
index 7291b507deac..ca2dbfa9b816 100644
--- a/lightningd/channel.h
+++ b/lightningd/channel.h
@@ -765,7 +765,7 @@ void channel_set_state(struct channel *channel,
 		       enum channel_state old_state,
 		       enum channel_state state,
 		       enum state_change reason,
-		       char *why);
+		       const char *why);
 
 const char *channel_change_state_reason_str(enum state_change reason);