diff --git a/content/treestyletab/config.js b/content/treestyletab/config.js
index d9633e60..71f423e8 100644
--- a/content/treestyletab/config.js
+++ b/content/treestyletab/config.js
@@ -233,7 +233,7 @@ function onChangeTabbarPosition()
 	gTabbarPlacePositionInitialized = true;
 }
 
-function onSyncMaxTreeLevelUIToPref(aTarget)
+function onSyncMaxTreeLevelUIToPref(aTarget, aSetPrefValue)
 {
 	aTarget = document.getElementById(aTarget);
 	if (aTarget.sync)
@@ -243,6 +243,9 @@ function onSyncMaxTreeLevelUIToPref(aTarget)
 	var textbox = aTarget.parentNode.getElementsByTagName('textbox')[0];
 	var prefValue = aTarget.checked ? textbox.value : 0 ;
 
+	if (aSetPrefValue)
+		document.getElementById(aTarget.getAttribute('preference')).value = prefValue;
+
 	aTarget.sync = false;
 	return prefValue;
 }
diff --git a/content/treestyletab/config.xul b/content/treestyletab/config.xul
index 762f58f5..47ff026a 100644
--- a/content/treestyletab/config.xul
+++ b/content/treestyletab/config.xul
@@ -143,8 +143,8 @@
 			<textbox id="maxTreeLevel-textbox-horizontal"
 				type="number"
 				min="1" increment="1" size="4"
-				value="999"
-				oninput="document.getElementById(this.previousSibling.previousSibling.getAttribute('preference')).value = this.value;"/>
+				oninput="onSyncMaxTreeLevelUIToPref('maxTreeLevel-checkbox-horizontal', true);"
+				onchange="onSyncMaxTreeLevelUIToPref('maxTreeLevel-checkbox-horizontal', true);"/>
 			<label control="maxTreeLevel-textbox-horizontal"
 				value="&config.maxTreeLevel.after;"/>
 		</hbox>
@@ -160,8 +160,8 @@
 			<textbox id="maxTreeLevel-textbox-vertical"
 				type="number"
 				min="1" increment="1" size="4"
-				value="999"
-				oninput="document.getElementById(this.previousSibling.previousSibling.getAttribute('preference')).value = this.value;"/>
+				oninput="onSyncMaxTreeLevelUIToPref('maxTreeLevel-checkbox-vertical', true);"
+				onchange="onSyncMaxTreeLevelUIToPref('maxTreeLevel-checkbox-vertical', true);"/>
 			<label control="maxTreeLevel-textbox-vertical"
 				value="&config.maxTreeLevel.after;"/>
 		</hbox>