diff --git a/container/docker/fsHandler.go b/container/docker/fsHandler.go
index 0792ebac..c5b406a4 100644
--- a/container/docker/fsHandler.go
+++ b/container/docker/fsHandler.go
@@ -67,15 +67,23 @@ func newFsHandler(period time.Duration, rootfs, extraDir string, fsInfo fs.FsInf
 }
 
 func (fh *realFsHandler) update() error {
+	var (
+		baseUsage, extraDirUsage uint64
+		err                      error
+	)
 	// TODO(vishh): Add support for external mounts.
-	baseUsage, err := fh.fsInfo.GetDirUsage(fh.rootfs, duTimeout)
-	if err != nil {
-		return err
+	if fh.rootfs != "" {
+		baseUsage, err = fh.fsInfo.GetDirUsage(fh.rootfs, duTimeout)
+		if err != nil {
+			return err
+		}
 	}
 
-	extraDirUsage, err := fh.fsInfo.GetDirUsage(fh.extraDir, duTimeout)
-	if err != nil {
-		return err
+	if fh.extraDir != "" {
+		extraDirUsage, err = fh.fsInfo.GetDirUsage(fh.extraDir, duTimeout)
+		if err != nil {
+			return err
+		}
 	}
 
 	fh.Lock()
diff --git a/fs/fs.go b/fs/fs.go
index 5d0489e7..02bda501 100644
--- a/fs/fs.go
+++ b/fs/fs.go
@@ -358,6 +358,9 @@ func (self *RealFsInfo) GetDirFsDevice(dir string) (*DeviceInfo, error) {
 }
 
 func (self *RealFsInfo) GetDirUsage(dir string, timeout time.Duration) (uint64, error) {
+	if dir == "" {
+		return 0, fmt.Errorf("invalid directory")
+	}
 	cmd := exec.Command("nice", "-n", "19", "du", "-s", dir)
 	stdoutp, err := cmd.StdoutPipe()
 	if err != nil {