diff --git a/README.md b/README.md
index 3b974cb..c05707e 100644
--- a/README.md
+++ b/README.md
@@ -37,6 +37,7 @@ Define in xml like this and make sure that the `RadioButton`'s style is: `@style
 <attr name="sc_border_width" format="dimension" />
 <attr name="sc_tint_color" format="color" />
 <attr name="sc_checked_text_color" format="color" />
+<attr name="sc_unchecked_tint_color" format="color"/>
 ```
 
 Sample code: