diff --git a/cmn/cos/io.go b/cmn/cos/io.go
index 14124dea774..1e426973a34 100644
--- a/cmn/cos/io.go
+++ b/cmn/cos/io.go
@@ -283,7 +283,7 @@ func NewCallbackReadOpenCloser(r ReadOpenCloser, readCb func(int, error), report
 
 func (r *CallbackROC) Read(p []byte) (n int, err error) {
 	n, err = r.roc.Read(p)
-	debug.Assert(r.readBytes > math.MaxInt-n)
+	debug.Assert(r.readBytes < math.MaxInt-n)
 	r.readBytes += n
 	if r.readBytes > r.reportedBytes {
 		diff := r.readBytes - r.reportedBytes
diff --git a/cmn/err.go b/cmn/err.go
index 907fb77355e..35abf2cbd6b 100644
--- a/cmn/err.go
+++ b/cmn/err.go
@@ -150,6 +150,9 @@ type (
 		disks   []string
 		fsdisks []string
 	}
+	ErrMountpathChangeRT struct {
+		err error
+	}
 
 	ErrInvalidFSPathsConf struct {
 		err error
@@ -583,6 +586,21 @@ func IsErrMountpathNewDisk(err error) bool {
 	return ok
 }
 
+// ErrMountpathChangeRT
+
+func NewErrMountpathChangeRT(err error) *ErrMountpathChangeRT {
+	return &ErrMountpathChangeRT{err: err}
+}
+
+func (e *ErrMountpathChangeRT) Error() string {
+	return e.err.Error()
+}
+
+func IsErrMountpathChangeRT(err error) bool {
+	_, ok := err.(*ErrMountpathChangeRT)
+	return ok
+}
+
 // ErrInvalidFSPathsConf
 
 func NewErrInvalidFSPathsConf(err error) *ErrInvalidFSPathsConf {
diff --git a/fs/fs.go b/fs/fs.go
index c368d912b59..8a91ad527f8 100644
--- a/fs/fs.go
+++ b/fs/fs.go
@@ -119,10 +119,21 @@ func NewMountpath(mpath string, label ios.Label) (*Mountpath, error) {
 		Label:      label,
 		PathDigest: xxhash.Checksum64S(cos.UnsafeB(cleanMpath), cos.MLCG32),
 	}
-	err = mi.ResolveFS()
+	err = mi.resolveFS()
 	return mi, err
 }
 
+func (mi *Mountpath) CheckFS() (err error) {
+	dup := Mountpath{Path: mi.Path}
+	err = dup.resolveFS()
+	if err == nil {
+		if !dup.FS.Equal(mi.FS) {
+			err = fmt.Errorf("%s: detected filesystem change at runtime: %s => %s ", mi, mi.FS.String(), dup.FS.String())
+		}
+	}
+	return err
+}
+
 // flags
 func (mi *Mountpath) SetFlags(flags uint64) (ok bool) {
 	return cos.SetfAtomic(&mi.flags, flags)
diff --git a/fs/fs_darwin.go b/fs/fs_darwin.go
index c841500430e..7fd4530ef35 100644
--- a/fs/fs_darwin.go
+++ b/fs/fs_darwin.go
@@ -10,7 +10,7 @@ import (
 	"syscall"
 )
 
-func (mi *Mountpath) ResolveFS() error {
+func (mi *Mountpath) resolveFS() error {
 	var fsStats syscall.Statfs_t
 	if err := syscall.Statfs(mi.Path, &fsStats); err != nil {
 		return fmt.Errorf("cannot statfs fspath %q, err: %w", mi.Path, err)
diff --git a/fs/fs_linux.go b/fs/fs_linux.go
index f6adf91de64..6a4b406419a 100644
--- a/fs/fs_linux.go
+++ b/fs/fs_linux.go
@@ -13,7 +13,7 @@ import (
 	"syscall"
 )
 
-func (mi *Mountpath) ResolveFS() error {
+func (mi *Mountpath) resolveFS() error {
 	var fsStats syscall.Statfs_t
 	if err := syscall.Statfs(mi.Path, &fsStats); err != nil {
 		return fmt.Errorf("cannot statfs fspath %q, err: %w", mi.Path, err)
diff --git a/fs/health/fshc.go b/fs/health/fshc.go
index 5f6190057ed..d4ffe227bf4 100644
--- a/fs/health/fshc.go
+++ b/fs/health/fshc.go
@@ -51,7 +51,6 @@ func (f *FSHC) run(mi *fs.Mountpath, fqn string) {
 		serr         string
 		rerrs, werrs int
 		cfg          = cmn.GCO.Get().FSHC
-		dup          = fs.Mountpath{Path: mi.Path}
 	)
 	// 1. fstat
 	err := cos.Stat(mi.Path)
@@ -65,13 +64,7 @@ func (f *FSHC) run(mi *fs.Mountpath, fqn string) {
 	}
 
 	// 2. resolve FS
-	err = dup.ResolveFS()
-	if err == nil {
-		if !dup.FS.Equal(mi.FS) {
-			err = fmt.Errorf("%s: detected filesystem change (%s => %s) at runtime", mi, mi.FS.String(), dup.FS.String())
-		}
-	}
-	if err != nil {
+	if err = mi.CheckFS(); err != nil {
 		nlog.Errorln(err)
 		goto disable
 	}
diff --git a/fs/health/serialize.go b/fs/health/serialize.go
index 3baa1dda550..5a17a16a4a8 100644
--- a/fs/health/serialize.go
+++ b/fs/health/serialize.go
@@ -26,7 +26,7 @@ type ror struct {
 var all sync.Map // [mpath => ror]
 
 func (*FSHC) IsErr(err error) bool {
-	return cmn.IsErrGetCap(err) || cos.IsIOError(err)
+	return cmn.IsErrGetCap(err) || cmn.IsErrMountpathChangeRT(err) || cos.IsIOError(err)
 }
 
 func (f *FSHC) OnErr(mi *fs.Mountpath, fqn string) {
diff --git a/fs/walkbck.go b/fs/walkbck.go
index e667afa4e96..39052b4c4d5 100644
--- a/fs/walkbck.go
+++ b/fs/walkbck.go
@@ -10,6 +10,7 @@ import (
 
 	"github.com/NVIDIA/aistore/cmn"
 	"github.com/NVIDIA/aistore/cmn/debug"
+	"github.com/NVIDIA/aistore/cmn/nlog"
 	"golang.org/x/sync/errgroup"
 )
 
@@ -43,6 +44,7 @@ type (
 	wbeHeap []wbeInfo
 )
 
+// lso and tests
 func WalkBck(opts *WalkBckOpts) error {
 	debug.Assert(opts.Mi == nil && opts.Sorted) // TODO: support `opts.Sorted == false`
 	var (
@@ -100,9 +102,14 @@ func WalkBck(opts *WalkBckOpts) error {
 ///////////////
 
 func (jg *joggerBck) walk() (err error) {
-	err = Walk(&jg.opts)
+	if err = jg.opts.Mi.CheckFS(); err != nil {
+		nlog.Errorln(err)
+		mfs.hc.FSHC(cmn.NewErrMountpathChangeRT(err), jg.opts.Mi, "")
+	} else {
+		err = Walk(&jg.opts)
+	}
 	close(jg.workCh)
-	return
+	return err
 }
 
 func (jg *joggerBck) cb(fqn string, de DirEntry) error {