diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index d82bc3fdb86e..43d8959cc746 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -383,6 +383,7 @@ int setup_one_line(struct line *lines, int n, char *init,
 			parse_chan_pair(NULL, line, n, opts, error_out);
 			err = 0;
 		}
+		*error_out = "configured as 'none'";
 	} else {
 		char *new = kstrdup(init, GFP_KERNEL);
 		if (!new) {
@@ -406,6 +407,7 @@ int setup_one_line(struct line *lines, int n, char *init,
 			}
 		}
 		if (err) {
+			*error_out = "failed to parse channel pair";
 			line->init_str = NULL;
 			line->valid = 0;
 			kfree(new);