diff --git a/cmd-queue.c b/cmd-queue.c
index 8a274305..7fe2793a 100644
--- a/cmd-queue.c
+++ b/cmd-queue.c
@@ -137,7 +137,14 @@ cmdq_error(struct cmd_q *cmdq, const char *fmt, ...)
 	va_end(ap);
 
 	if (c == NULL) {
+#ifdef TMATE
+		if (cmd->file && cmd->line)
+			xasprintf(&cause, "%s:%u: %s", cmd->file, cmd->line, msg);
+		else
+			xasprintf(&cause, "%s", msg);
+#else
 		xasprintf(&cause, "%s:%u: %s", cmd->file, cmd->line, msg);
+#endif
 		ARRAY_ADD(&cfg_causes, cause);
 	} else if (c->session == NULL || (c->flags & CLIENT_CONTROL)) {
 		evbuffer_add(c->stderr_data, msg, msglen);
@@ -228,7 +235,7 @@ cmdq_continue(struct cmd_q *cmdq)
 
 #ifdef TMATE
 			if (tmate_should_replicate_cmd(cmdq->cmd->entry))
-				tmate_cmd(s);
+				tmate_exec_cmd(s);
 #endif
 
 			guard = cmdq_guard(cmdq, "begin");
diff --git a/tmate-decoder.c b/tmate-decoder.c
index 00c4890f..0bdca7d4 100644
--- a/tmate-decoder.c
+++ b/tmate-decoder.c
@@ -115,23 +115,36 @@ static void tmate_client_resize(struct tmate_unpacker *uk)
 	/* TODO Handle reconnection cases */
 }
 
-static void tmate_client_cmd(struct tmate_unpacker *uk)
+static void tmate_client_exec_cmd(struct tmate_unpacker *uk)
 {
 	struct cmd_q *cmd_q;
 	struct cmd_list *cmdlist;
-	char *cmd_str;
 	char *cause;
 
-	cmd_str = unpack_string(uk);
+	int client_id = unpack_int(uk);
+	char *cmd_str = unpack_string(uk);
+
 	if (cmd_string_parse(cmd_str, &cmdlist, NULL, 0, &cause) != 0) {
+		tmate_failed_cmd(client_id, cause);
 		free(cause);
 		goto out;
 	}
 
+	/* error messages land in cfg_causes */
+	ARRAY_FREE(&cfg_causes);
+
 	cmd_q = cmdq_new(NULL);
 	cmdq_run(cmd_q, cmdlist);
 	cmd_list_free(cmdlist);
 	cmdq_free(cmd_q);
+
+	if (!ARRAY_EMPTY(&cfg_causes)) {
+		cause = ARRAY_ITEM(&cfg_causes, 0);
+		tmate_failed_cmd(client_id, cause);
+		free(cause);
+		ARRAY_FREE(&cfg_causes);
+	}
+
 out:
 	free(cmd_str);
 }
@@ -148,7 +161,7 @@ static void handle_message(msgpack_object obj)
 	case TMATE_REPLY_HEADER:	tmate_reply_header(uk); break;
 	case TMATE_CLIENT_PANE_KEY:	tmate_client_pane_key(uk); break;
 	case TMATE_CLIENT_RESIZE:	tmate_client_resize(uk); break;
-	case TMATE_CLIENT_CMD:		tmate_client_cmd(uk); break;
+	case TMATE_CLIENT_EXEC_CMD:	tmate_client_exec_cmd(uk); break;
 	default:			decoder_error();
 	}
 }
diff --git a/tmate-encoder.c b/tmate-encoder.c
index cf5d1e29..0e4a2c09 100644
--- a/tmate-encoder.c
+++ b/tmate-encoder.c
@@ -147,13 +147,21 @@ int tmate_should_replicate_cmd(const struct cmd_entry *cmd)
 	return 0;
 }
 
-void tmate_cmd(const char *cmd)
+void tmate_exec_cmd(const char *cmd)
 {
 	pack(array, 2);
-	pack(int, TMATE_CMD);
+	pack(int, TMATE_EXEC_CMD);
 	pack(string, cmd);
 }
 
+void tmate_failed_cmd(int client_id, const char *cause)
+{
+	pack(array, 3);
+	pack(int, TMATE_FAILED_CMD);
+	pack(int, client_id);
+	pack(string, cause);
+}
+
 void tmate_status(const char *left, const char *right)
 {
 	static char *old_left, *old_right;
diff --git a/tmate.h b/tmate.h
index 612fc184..0ff4cd23 100644
--- a/tmate.h
+++ b/tmate.h
@@ -22,7 +22,8 @@ enum tmate_commands {
 	TMATE_HEADER,
 	TMATE_SYNC_LAYOUT,
 	TMATE_PTY_DATA,
-	TMATE_CMD,
+	TMATE_EXEC_CMD,
+	TMATE_FAILED_CMD,
 	TMATE_STATUS,
 };
 
@@ -38,7 +39,8 @@ extern void tmate_write_header(void);
 extern void tmate_sync_layout(void);
 extern void tmate_pty_data(struct window_pane *wp, const char *buf, size_t len);
 extern int tmate_should_replicate_cmd(const struct cmd_entry *cmd);
-extern void tmate_cmd(const char *cmd);
+extern void tmate_exec_cmd(const char *cmd);
+extern void tmate_failed_cmd(int client_id, const char *cause);
 extern void tmate_status(const char *left, const char *right);
 
 /* tmate-decoder.c */
@@ -47,7 +49,7 @@ enum tmate_client_commands {
 	TMATE_REPLY_HEADER,
 	TMATE_CLIENT_PANE_KEY,
 	TMATE_CLIENT_RESIZE,
-	TMATE_CLIENT_CMD,
+	TMATE_CLIENT_EXEC_CMD,
 };
 
 struct tmate_decoder {