diff --git a/forms/OptionsetField.php b/forms/OptionsetField.php
index 5f25bb7fc..9f8033a5f 100755
--- a/forms/OptionsetField.php
+++ b/forms/OptionsetField.php
@@ -44,7 +44,7 @@ class OptionsetField extends DropdownField {
 			
 			$odd = ($odd + 1) % 2;
 			$extraClass = $odd ? "odd" : "even";
-			$extraClass .= " val" . str_replace(' ','',$key);
+			$extraClass .= " val" . preg_replace('/[^a-zA-Z0-9\-\_]/','_', $key);
 			$disabled = $this->disabled ? 'disabled="disabled"' : '';
 			
 			$options .= "<li class=\"".$extraClass."\"><input id=\"$itemID\" name=\"$this->name\" type=\"radio\" value=\"$key\"$checked $disabled/> <label for=\"$itemID\">$value</label></li>\n";