diff --git a/man2/ioctl_ficlonerange.2 b/man2/ioctl_ficlonerange.2
index 0cb15670e..c6e0762a3 100644
--- a/man2/ioctl_ficlonerange.2
+++ b/man2/ioctl_ficlonerange.2
@@ -36,6 +36,7 @@ file appear in the
 .I dest_fd
 file by sharing the underlying storage, which is faster than making a separate
 physical copy of the data.
+Both files must reside within the same filesystem.
 If a file write should occur to a shared region,
 the filesystem must ensure that the changes remain private to the file being
 written.
diff --git a/man2/ioctl_fideduperange.2 b/man2/ioctl_fideduperange.2
index c69f8c531..44a7765a8 100644
--- a/man2/ioctl_fideduperange.2
+++ b/man2/ioctl_fideduperange.2
@@ -34,6 +34,7 @@ file appear in the
 .B dest_fd
 file by sharing the underlying storage if the file data is identical
 ("deduplication").
+Both files must reside within the same filesystem.
 This reduces storage consumption by allowing the filesystem
 to store one shared copy of the data.
 If a file write should occur to a shared