diff --git a/storage/storagedriver/overlayfs-driver.md b/storage/storagedriver/overlayfs-driver.md
index 0ca1928910..3c8092dd18 100644
--- a/storage/storagedriver/overlayfs-driver.md
+++ b/storage/storagedriver/overlayfs-driver.md
@@ -269,7 +269,7 @@ for `overlay2`.
 
 OverlayFS layers two directories on a single Linux host and presents them as
 a single directory. These directories are called _layers_ and the unification
-process is referred to as _union mount_. OverlayFS refers to the lower directory
+process is referred to as a _union mount_. OverlayFS refers to the lower directory
 as `lowerdir` and the upper directory a `upperdir`. The unified view is exposed
 through its own directory called `merged`.