diff --git a/bash_completions.go b/bash_completions.go
index 735d2f5..3a421bc 100644
--- a/bash_completions.go
+++ b/bash_completions.go
@@ -219,9 +219,13 @@ func writeFlagHandler(name string, annotations map[string][]string, out *bytes.B
 		case BashCompFilenameExt:
 			fmt.Fprintf(out, "    flags_with_completion+=(%q)\n", name)
 
-			ext := strings.Join(value, "|")
-			ext = "__handle_filename_extension_flag " + ext
-			fmt.Fprintf(out, "    flags_completion+=(%q)\n", ext)
+			if len(value) > 0 {
+				ext := "__handle_filename_extension_flag " + strings.Join(value, "|")
+				fmt.Fprintf(out, "    flags_completion+=(%q)\n", ext)
+			} else {
+				ext := "_filedir"
+				fmt.Fprintf(out, "    flags_completion+=(%q)\n", ext)
+			}
 		}
 	}
 }
@@ -343,15 +347,24 @@ func (cmd *Command) GenBashCompletionFile(filename string) error {
 	return nil
 }
 
-func (cmd *Command) MarkFlagRequired(name string) {
-	flag := cmd.Flags().Lookup(name)
-	if flag == nil {
-		return
-	}
-	if flag.Annotations == nil {
-		flag.Annotations = make(map[string][]string)
-	}
-	annotation := make([]string, 1)
-	annotation[0] = "true"
-	flag.Annotations[BashCompOneRequiredFlag] = annotation
+// MarkFlagRequired adds the BashCompOneRequiredFlag annotation to the named flag, if it exists.
+func (cmd *Command) MarkFlagRequired(name string) error {
+	return MarkFlagRequired(cmd.Flags(), name)
+}
+
+// MarkFlagRequired adds the BashCompOneRequiredFlag annotation to the named flag in the flag set, if it exists.
+func MarkFlagRequired(flags *pflag.FlagSet, name string) error {
+	return flags.SetAnnotation(name, BashCompOneRequiredFlag, []string{"true"})
+}
+
+// MarkFlagFilename adds the BashCompFilenameExt annotation to the named flag, if it exists.
+// Generated bash autocompletion will select filenames for the flag, limiting to named extensions if provided.
+func (cmd *Command) MarkFlagFilename(name string, extensions ...string) error {
+	return MarkFlagFilename(cmd.Flags(), name, extensions...)
+}
+
+// MarkFlagFilename adds the BashCompFilenameExt annotation to the named flag in the flag set, if it exists.
+// Generated bash autocompletion will select filenames for the flag, limiting to named extensions if provided.
+func MarkFlagFilename(flags *pflag.FlagSet, name string, extensions ...string) error {
+	return flags.SetAnnotation(name, BashCompFilenameExt, extensions)
 }
diff --git a/bash_completions_test.go b/bash_completions_test.go
index ee632cf..acb6d81 100644
--- a/bash_completions_test.go
+++ b/bash_completions_test.go
@@ -42,23 +42,19 @@ func TestBashCompletions(t *testing.T) {
 	// required flag
 	c.MarkFlagRequired("introot")
 
-	// valid nounds
+	// valid nouns
 	validArgs := []string{"pods", "nodes", "services", "replicationControllers"}
 	c.ValidArgs = validArgs
 
-	// filename extentions
-	annotations := make([]string, 3)
-	annotations[0] = "json"
-	annotations[1] = "yaml"
-	annotations[2] = "yml"
-
-	annotation := make(map[string][]string)
-	annotation[BashCompFilenameExt] = annotations
-
+	// filename
 	var flagval string
 	c.Flags().StringVar(&flagval, "filename", "", "Enter a filename")
-	flag := c.Flags().Lookup("filename")
-	flag.Annotations = annotation
+	c.MarkFlagFilename("filename", "json", "yaml", "yml")
+
+	// filename extensions
+	var flagvalExt string
+	c.Flags().StringVar(&flagvalExt, "filename-ext", "", "Enter a filename (extension limited)")
+	c.MarkFlagFilename("filename-ext")
 
 	out := new(bytes.Buffer)
 	c.GenBashCompletion(out)
@@ -75,7 +71,9 @@ func TestBashCompletions(t *testing.T) {
 	check(t, str, `COMPREPLY=( "hello" )`)
 	// check for required nouns
 	check(t, str, `must_have_one_noun+=("pods")`)
-	// check for filename extention flags
+	// check for filename extension flags
+	check(t, str, `flags_completion+=("_filedir")`)
+	// check for filename extension flags
 	check(t, str, `flags_completion+=("__handle_filename_extension_flag json|yaml|yml")`)
 
 	checkOmit(t, str, cmdDeprecated.Name())