diff --git a/container/common/helpers.go b/container/common/helpers.go
index 33d9db37..f5539b5d 100644
--- a/container/common/helpers.go
+++ b/container/common/helpers.go
@@ -127,15 +127,13 @@ func GetSpec(cgroupPaths map[string]string, machineInfoFactory info.MachineInfoF
 func readString(dirpath string, file string) string {
 	cgroupFile := path.Join(dirpath, file)
 
-	// Ignore non-existent files
-	if !utils.FileExists(cgroupFile) {
-		return ""
-	}
-
 	// Read
 	out, err := ioutil.ReadFile(cgroupFile)
 	if err != nil {
-		glog.Errorf("readString: Failed to read %q: %s", cgroupFile, err)
+		// Ignore non-existent files
+		if !os.IsNotExist(err) {
+			glog.Errorf("readString: Failed to read %q: %s", cgroupFile, err)
+		}
 		return ""
 	}
 	return strings.TrimSpace(string(out))
@@ -158,13 +156,12 @@ func readUInt64(dirpath string, file string) uint64 {
 
 // Lists all directories under "path" and outputs the results as children of "parent".
 func ListDirectories(dirpath string, parent string, recursive bool, output map[string]struct{}) error {
-	// Ignore if this hierarchy does not exist.
-	if !utils.FileExists(dirpath) {
-		return nil
-	}
-
 	entries, err := ioutil.ReadDir(dirpath)
 	if err != nil {
+		// Ignore if this hierarchy does not exist.
+		if os.IsNotExist(err) {
+			err = nil
+		}
 		return err
 	}
 	for _, entry := range entries {