diff --git a/metropolis/pkg/event/etcd/etcd.go b/metropolis/pkg/event/etcd/etcd.go
index 14dfd99..71e8056 100644
--- a/metropolis/pkg/event/etcd/etcd.go
+++ b/metropolis/pkg/event/etcd/etcd.go
@@ -402,7 +402,7 @@
 	}
 
 	if backlogOnly && len(w.backlogged) == 0 {
-		return empty, event.BacklogDone
+		return empty, event.ErrBacklogDone
 	}
 
 	// Update backlog from etcd if needed.
diff --git a/metropolis/pkg/event/etcd/etcd_test.go b/metropolis/pkg/event/etcd/etcd_test.go
index 45b5f98..f1eb5ed 100644
--- a/metropolis/pkg/event/etcd/etcd_test.go
+++ b/metropolis/pkg/event/etcd/etcd_test.go
@@ -776,15 +776,15 @@
 	// As expected, next call to Get with BacklogOnly fails - there truly is no new
 	// updates to emit.
 	_, err = watcher.Get(ctx, event.BacklogOnly[StringAt]())
-	if want, got := event.BacklogDone, err; !errors.Is(got, want) {
+	if want, got := event.ErrBacklogDone, err; !errors.Is(got, want) {
 		t.Fatalf("Second Get: wanted %v, got %v", want, got)
 	}
 
 	// Implementation detail: even though there is a new value ('second'),
-	// BacklogOnly will still return BacklogDone.
+	// BacklogOnly will still return ErrBacklogDone.
 	tc.put(t, k, "second")
 	_, err = watcher.Get(ctx, event.BacklogOnly[StringAt]())
-	if want, got := event.BacklogDone, err; !errors.Is(got, want) {
+	if want, got := event.ErrBacklogDone, err; !errors.Is(got, want) {
 		t.Fatalf("Third Get: wanted %v, got %v", want, got)
 	}
 
@@ -836,11 +836,11 @@
 	tc.put(t, ks+"a", "val-100")
 	tc.put(t, ks+"b", "val-101")
 
-	// Retrieve the rest of the backlog until BacklogDone is returned.
+	// Retrieve the rest of the backlog until ErrBacklogDone is returned.
 	nUpdates := 1
 	for {
 		g, err := w.Get(ctx, event.BacklogOnly[StringAt]())
-		if errors.Is(err, event.BacklogDone) {
+		if errors.Is(err, event.ErrBacklogDone) {
 			break
 		}
 		if err != nil {
diff --git a/metropolis/pkg/event/event.go b/metropolis/pkg/event/event.go
index e38c427..a8b3526 100644
--- a/metropolis/pkg/event/event.go
+++ b/metropolis/pkg/event/event.go
@@ -179,7 +179,7 @@
 }
 
 // BacklogOnly will prevent Get from blocking on waiting for more updates from
-// etcd, by instead returning BacklogDone whenever no more data is currently
+// etcd, by instead returning ErrBacklogDone whenever no more data is currently
 // locally available. This is different however, from establishing that there
 // are no more pending updates from the etcd cluster - the only way to ensure
 // the local client is up to date is by performing Get calls without this option
@@ -187,7 +187,7 @@
 //
 // This mode of retrieval should only be used for the retrieval of the existing
 // data in the etcd cluster on the initial creation of the Watcher (by
-// repeatedly calling Get until BacklogDone is returned), and shouldn't be set
+// repeatedly calling Get until ErrBacklogDone is returned), and shouldn't be set
 // for any subsequent call. Any use of this option after that initial fetch is
 // undefined behaviour that exposes the internals of the Get implementation, and
 // must not be relied on. However, in the future, this behaviour might be
@@ -203,10 +203,10 @@
 }
 
 var (
-	// BacklogDone is returned by Get when BacklogOnly is set and there is no more
+	// ErrBacklogDone is returned by Get when BacklogOnly is set and there is no more
 	// event data stored in the Watcher client, ie. when the initial cluster state
 	// of the requested key has been retrieved.
-	BacklogDone = errors.New("no more backlogged data")
+	ErrBacklogDone = errors.New("no more backlogged data")
 )
 
 // Pipe a Value's initial state and subsequent updates to an already existing