diff --git a/backend/combine/combine.go b/backend/combine/combine.go
index 2e1ad2a7b..2457bc4f1 100644
--- a/backend/combine/combine.go
+++ b/backend/combine/combine.go
@@ -299,6 +299,9 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (outFs fs
 		}
 	}
 
+	// show that we wrap other backends
+	features.Overlay = true
+
 	f.features = features
 
 	// Get common intersection of hashes
diff --git a/backend/union/union.go b/backend/union/union.go
index 1b3c0f4db..78a713896 100644
--- a/backend/union/union.go
+++ b/backend/union/union.go
@@ -914,6 +914,9 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, e
 		}
 	}
 
+	// show that we wrap other backends
+	features.Overlay = true
+
 	f.features = features
 
 	// Get common intersection of hashes
diff --git a/fs/features.go b/fs/features.go
index 2ba54abe2..4c3612285 100644
--- a/fs/features.go
+++ b/fs/features.go
@@ -32,6 +32,7 @@ type Features struct {
 	FilterAware             bool // can make use of filters if provided for listing
 	PartialUploads          bool // uploaded file can appear incomplete on the fs while it's being uploaded
 	NoMultiThreading        bool // set if can't have multiplethreads on one download open
+	Overlay                 bool // this wraps one or more backends to add functionality
 
 	// Purge all files in the directory specified
 	//
@@ -271,6 +272,7 @@ func (ft *Features) Fill(ctx context.Context, f Fs) *Features {
 	if do, ok := f.(Wrapper); ok {
 		ft.WrapFs = do.WrapFs
 		ft.SetWrapper = do.SetWrapper
+		ft.Overlay = true // if implement UnWrap then must be an Overlay
 	}
 	if do, ok := f.(DirCacheFlusher); ok {
 		ft.DirCacheFlush = do.DirCacheFlush
@@ -339,6 +341,9 @@ func (ft *Features) Mask(ctx context.Context, f Fs) *Features {
 	ft.SlowModTime = ft.SlowModTime && mask.SlowModTime
 	ft.SlowHash = ft.SlowHash && mask.SlowHash
 	ft.FilterAware = ft.FilterAware && mask.FilterAware
+	ft.PartialUploads = ft.PartialUploads && mask.PartialUploads
+	ft.NoMultiThreading = ft.NoMultiThreading && mask.NoMultiThreading
+	// ft.Overlay = ft.Overlay && mask.Overlay don't propagate Overlay
 
 	if mask.Purge == nil {
 		ft.Purge = nil
diff --git a/fstest/fstests/fstests.go b/fstest/fstests/fstests.go
index 46a6ff4b5..ddd20c97a 100644
--- a/fstest/fstests/fstests.go
+++ b/fstest/fstests/fstests.go
@@ -460,7 +460,7 @@ func Run(t *testing.T, opt *Opt) {
 			t.Skip("Skipping FsCheckWrap on this Fs")
 		}
 		ft := new(fs.Features).Fill(ctx, f)
-		if ft.UnWrap == nil {
+		if ft.UnWrap == nil && !f.Features().Overlay {
 			t.Skip("Not a wrapping Fs")
 		}
 		v := reflect.ValueOf(ft).Elem()