diff --git a/plainText.go b/plainText.go
index 149fcd2..ff13bbc 100644
--- a/plainText.go
+++ b/plainText.go
@@ -8,7 +8,7 @@ type PlainText struct {
 	Text string `xml:"text"`
 }
 
-func (p *PlainText) IsText() bool { return true }
+func (p *PlainText) isText() bool { return true }
 
 func (p *PlainText) Check() error {
 	if p.Type != "" && p.Type != "text" && p.Type != "html" {
diff --git a/text.go b/text.go
index 96c548d..15004df 100644
--- a/text.go
+++ b/text.go
@@ -6,8 +6,8 @@ import (
 )
 
 type Text interface {
+	isText() bool
 	Check() error
-	IsText() bool
 }
 
 func NewText(textType, content string) (Text, error) {
diff --git a/xhtmlText.go b/xhtmlText.go
index 9965738..82157f7 100644
--- a/xhtmlText.go
+++ b/xhtmlText.go
@@ -17,7 +17,7 @@ type XHTMLText struct {
 	XHTMLDiv XHTMLDiv
 }
 
-func (x *XHTMLText) IsText() bool { return true }
+func (x *XHTMLText) isText() bool { return true }
 
 func (x *XHTMLText) Check() error {
 	if x.Type != "xhtml" {