diff --git a/include/usage.h b/include/usage.h
index 05fd23129..9390e3415 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -1696,7 +1696,8 @@
 #define mount_trivial_usage \
 	"[flags] DEVICE NODE [-o options,more-options]"
 #define mount_full_usage \
-	"Mount a filesystem\n\n" \
+	"Mount a filesystem.  Autodetection of filesystem type requires the\n" \
+	"/proc filesystem be already mounted.\n\n" \
 	"Flags:\n"  \
 	"\t-a:\t\tMount all filesystems in fstab.\n" \
 	USAGE_MTAB( \