diff --git a/phpBB/adm/style/editor.js b/phpBB/adm/style/editor.js
index 8d6df9164a..cd4e75f51f 100644
--- a/phpBB/adm/style/editor.js
+++ b/phpBB/adm/style/editor.js
@@ -258,7 +258,7 @@ function addquote(post_id, username)
 */
 function mozWrap(txtarea, open, close)
 {
-	var selLength = txtarea.textLength;
+	var selLength = (typeof(txtarea.textLength) == 'undefined') ? txtarea.value.length : txtarea.textLength;
 	var selStart = txtarea.selectionStart;
 	var selEnd = txtarea.selectionEnd;
 	var scrollTop = txtarea.scrollTop;
diff --git a/phpBB/styles/prosilver/template/editor.js b/phpBB/styles/prosilver/template/editor.js
index 639b87e3ee..1699f783d5 100644
--- a/phpBB/styles/prosilver/template/editor.js
+++ b/phpBB/styles/prosilver/template/editor.js
@@ -308,7 +308,7 @@ function split_lines(text)
 */
 function mozWrap(txtarea, open, close)
 {
-	var selLength = txtarea.textLength;
+	var selLength = (typeof(txtarea.textLength) == 'undefined') ? txtarea.value.length : txtarea.textLength;
 	var selStart = txtarea.selectionStart;
 	var selEnd = txtarea.selectionEnd;
 	var scrollTop = txtarea.scrollTop;
diff --git a/phpBB/styles/subsilver2/template/editor.js b/phpBB/styles/subsilver2/template/editor.js
index ae062d65a7..b4a426df4e 100644
--- a/phpBB/styles/subsilver2/template/editor.js
+++ b/phpBB/styles/subsilver2/template/editor.js
@@ -261,7 +261,7 @@ function addquote(post_id, username)
 */
 function mozWrap(txtarea, open, close)
 {
-	var selLength = txtarea.textLength;
+	var selLength = (typeof(txtarea.textLength) == 'undefined') ? txtarea.value.length : txtarea.textLength;
 	var selStart = txtarea.selectionStart;
 	var selEnd = txtarea.selectionEnd;
 	var scrollTop = txtarea.scrollTop;