diff --git a/diff/proxy/differ.go b/diff/proxy/differ.go
index 8ed8bdf4d..f0e547f81 100644
--- a/diff/proxy/differ.go
+++ b/diff/proxy/differ.go
@@ -100,6 +100,9 @@ func (r *diffRemote) Compare(ctx context.Context, a, b []mount.Mount, opts ...di
 }
 
 func toDescriptor(d *types.Descriptor) ocispec.Descriptor {
+	if d == nil {
+		return ocispec.Descriptor{}
+	}
 	return ocispec.Descriptor{
 		MediaType:   d.MediaType,
 		Digest:      digest.Digest(d.Digest),