diff --git a/metrics/metrics_client.cc b/metrics/metrics_client.cc
index 6819e1d..bbe9dcd 100644
--- a/metrics/metrics_client.cc
+++ b/metrics/metrics_client.cc
@@ -30,7 +30,8 @@
           "           |min| > 0, |min| <= sample < |max|\n"
           "  -a: send metric (name/sample) to Autotest only\n"
           "  -b: send metric to both Chrome and Autotest\n"
-          "  -c: return exit status 0 if user consents to stats, 1 otherwise\n"
+          "  -c: return exit status 0 if user consents to stats, 1 otherwise,\n"
+          "      in guest mode always return 1\n"
           "  -e: send linear/enumeration histogram data\n"
           "  -g: return exit status 0 if machine in guest mode, 1 otherwise\n"
           "  -s: send a sparse histogram sample\n"