diff --git a/Documentation/mkfs.btrfs.rst b/Documentation/mkfs.btrfs.rst
index 2ff3ed24..c0fd92f7 100644
--- a/Documentation/mkfs.btrfs.rst
+++ b/Documentation/mkfs.btrfs.rst
@@ -179,8 +179,9 @@ OPTIONS
         Resets any previous effects of *--verbose*.
 
 -U|--uuid <UUID>
-        Create the filesystem with the given *UUID*. The UUID must not exist on any
-        filesystem currently present.
+        Create the filesystem with the given *UUID*. For a single-device filesystem,
+        you can duplicate the UUID. However, for a multi-device filesystem, the UUID
+        must not already exist on any currently present filesystem.
 
 -v|--verbose
         Increase verbosity level, default is 1.
diff --git a/mkfs/main.c b/mkfs/main.c
index 7cb9fb48..4f6223ab 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -430,7 +430,7 @@ static const char * const mkfs_usage[] = {
 	OPTLINE("-s|--sectorsize SIZE", "data block size (may not be mountable by current kernel)"),
 	OPTLINE("-O|--features LIST", "comma separated list of filesystem features (use '-O list-all' to list features)"),
 	OPTLINE("-L|--label LABEL", "set the filesystem label"),
-	OPTLINE("-U|--uuid UUID", "specify the filesystem UUID (must be unique)"),
+	OPTLINE("-U|--uuid UUID", "specify the filesystem UUID (must be unique for a filesystem with multiple devices)"),
 	"Creation:",
 	OPTLINE("-b|--byte-count SIZE", "set size of each device to SIZE (filesystem size is sum of all device sizes)"),
 	OPTLINE("-r|--rootdir DIR", "copy files from DIR to the image root directory"),