diff --git a/nav.go b/nav.go
index 5dee4dd..a69bb1f 100644
--- a/nav.go
+++ b/nav.go
@@ -554,6 +554,34 @@ func (nav *nav) previewLoop(ui *ui) {
 	}
 }
 
+func isDirty(f os.FileInfo, path string, dirtyfiles []string) bool {
+	dirty := false
+	for _, pattern := range dirtyfiles {
+		matched := matchPattern(strings.TrimPrefix(pattern, "!"), f.Name(), path)
+		if strings.HasPrefix(pattern, "!") && matched {
+			dirty = false
+		} else if matched {
+			dirty = true
+		}
+	}
+	return dirty
+}
+
+func matchPattern(pattern, name, path string) bool {
+	s := name
+
+	pattern = replaceTilde(pattern)
+
+	if filepath.IsAbs(pattern) {
+		s = filepath.Join(path, name)
+	}
+
+	// pattern errors are checked when 'hiddenfiles' option is set
+	matched, _ := filepath.Match(pattern, s)
+
+	return matched
+}
+
 func (nav *nav) preview(path string, win *win) {
 	reg := &reg{loadTime: time.Now(), path: path}
 	defer func() { nav.regChan <- reg }()
diff --git a/os.go b/os.go
index fa20879..a434d1e 100644
--- a/os.go
+++ b/os.go
@@ -136,19 +136,6 @@ func isHidden(f os.FileInfo, path string, hiddenfiles []string) bool {
 	return hidden
 }
 
-func isDirty(f os.FileInfo, path string, dirtyfiles []string) bool {
-	dirty := false
-	for _, pattern := range dirtyfiles {
-		matched := matchPattern(strings.TrimPrefix(pattern, "!"), f.Name(), path)
-		if strings.HasPrefix(pattern, "!") && matched {
-			dirty = false
-		} else if matched {
-			dirty = true
-		}
-	}
-	return dirty
-}
-
 func userName(f os.FileInfo) string {
 	if stat, ok := f.Sys().(*syscall.Stat_t); ok {
 		if u, err := user.LookupId(fmt.Sprint(stat.Uid)); err == nil {
@@ -174,21 +161,6 @@ func linkCount(f os.FileInfo) string {
 	return ""
 }
 
-func matchPattern(pattern, name, path string) bool {
-	s := name
-
-	pattern = replaceTilde(pattern)
-
-	if filepath.IsAbs(pattern) {
-		s = filepath.Join(path, name)
-	}
-
-	// pattern errors are checked when 'hiddenfiles' option is set
-	matched, _ := filepath.Match(pattern, s)
-
-	return matched
-}
-
 func errCrossDevice(err error) bool {
 	return err.(*os.LinkError).Err.(syscall.Errno) == syscall.EXDEV
 }