diff --git a/control/control.go b/control/control.go
index a54425168..dd03c7567 100644
--- a/control/control.go
+++ b/control/control.go
@@ -311,6 +311,7 @@ func (c *Controller) ListenBuildHistory(req *controlapi.BuildHistoryRequest, srv
 
 func (c *Controller) UpdateBuildHistory(ctx context.Context, req *controlapi.UpdateBuildHistoryRequest) (*controlapi.UpdateBuildHistoryResponse, error) {
 	if req.Delete {
+		c.history.Finalize(ctx, req.Ref) // ignore error
 		err := c.history.Delete(ctx, req.Ref)
 		return &controlapi.UpdateBuildHistoryResponse{}, err
 	}
diff --git a/snapshot/containerd/content.go b/snapshot/containerd/content.go
index c50cc99ac..efbd9db6d 100644
--- a/snapshot/containerd/content.go
+++ b/snapshot/containerd/content.go
@@ -115,7 +115,20 @@ func (c *nsFallbackStore) Update(ctx context.Context, info content.Info, fieldpa
 }
 
 func (c *nsFallbackStore) Walk(ctx context.Context, fn content.WalkFunc, filters ...string) error {
-	return c.main.Walk(ctx, fn, filters...)
+	seen := make(map[digest.Digest]struct{})
+	err := c.main.Walk(ctx, func(i content.Info) error {
+		seen[i.Digest] = struct{}{}
+		return fn(i)
+	}, filters...)
+	if err != nil {
+		return err
+	}
+	return c.fb.Walk(ctx, func(i content.Info) error {
+		if _, ok := seen[i.Digest]; ok {
+			return nil
+		}
+		return fn(i)
+	}, filters...)
 }
 
 func (c *nsFallbackStore) Delete(ctx context.Context, dgst digest.Digest) error {