diff --git a/xC-proto b/xC-proto
index 7b77e5d..52bab54 100644
--- a/xC-proto
+++ b/xC-proto
@@ -63,6 +63,7 @@ struct EventMessage {
 		void;
 	case BUFFER_UPDATE:
 		string buffer_name;
+		bool hide_unimportant;
 	case BUFFER_STATS:
 		string buffer_name;
 		// These are cumulative, even for lines flushed out from buffers.
diff --git a/xC.c b/xC.c
index c440abc..1399744 100644
--- a/xC.c
+++ b/xC.c
@@ -3068,6 +3068,7 @@ relay_prepare_buffer_update (struct app_context *ctx, struct buffer *buffer)
 	struct relay_event_data_buffer_update *e = &m->data.buffer_update;
 	e->event = RELAY_EVENT_BUFFER_UPDATE;
 	e->buffer_name = str_from_cstr (buffer->name);
+	e->hide_unimportant = buffer->hide_unimportant;
 }
 
 static void
@@ -14202,6 +14203,10 @@ on_toggle_unimportant (int count, int key, void *user_data)
 	(void) key;
 	struct app_context *ctx = user_data;
 	ctx->current_buffer->hide_unimportant ^= true;
+
+	relay_prepare_buffer_update (ctx, ctx->current_buffer);
+	relay_broadcast (ctx);
+
 	buffer_print_backlog (ctx, ctx->current_buffer);
 	return true;
 }
diff --git a/xP/public/xP.js b/xP/public/xP.js
index 864323a..2e7732e 100644
--- a/xP/public/xP.js
+++ b/xP/public/xP.js
@@ -171,6 +171,7 @@ rpc.addEventListener('BufferUpdate', event => {
 		buffers.set(e.bufferName, (b = {lines: []}))
 		resetBufferStats(b)
 	}
+	b.hideUnimportant = e.hideUnimportant
 })
 
 rpc.addEventListener('BufferStats', event => {
@@ -465,6 +466,11 @@ let Buffer = {
 		let markBefore = b.lines.length
 			- b.newMessages - b.newUnimportantMessages
 		b.lines.forEach((line, i) => {
+			if (i == markBefore)
+				lines.push(m('.unread'))
+			if (line.isUnimportant && b.hideUnimportant)
+				return
+
 			let date = new Date(line.when)
 			let dateMark = date.toLocaleDateString()
 			if (dateMark !== lastDateMark) {
@@ -472,14 +478,10 @@ let Buffer = {
 				lastDateMark = dateMark
 			}
 
-			if (i == markBefore)
-				lines.push(m('.unread'))
-
 			let attrs = {}
 			if (line.leaked)
 				attrs.class = 'leaked'
 
-			// TODO: Make use of isUnimportant.
 			lines.push(m('.time', {...attrs}, date.toLocaleTimeString()))
 			lines.push(m(Content, {...attrs}, line))
 		})
@@ -604,6 +606,7 @@ let Main = {
 		return m('.xP', {}, [
 			m('.title', {}, [`xP (${state})`, m(Toolbar)]),
 			m('.middle', {}, [m(BufferList), m(BufferContainer)]),
+			// TODO: Indicate hideUnimportant.
 			m('.status', {}, bufferCurrent),
 			m(Input),
 		])