diff --git a/lam/lib/baseModule.inc b/lam/lib/baseModule.inc
index ac9d3996..4e2c8f90 100644
--- a/lam/lib/baseModule.inc
+++ b/lam/lib/baseModule.inc
@@ -1354,9 +1354,10 @@ abstract class baseModule {
 	 * @param array $autoCompleteValues values for auto-completion
 	 * @param integer $fieldSize field size
 	 * @param array $htmlIDs reference to array where to add the generated HTML IDs of the input fields
+	 * @param string $cssClasses additional CSS classes of input fields
 	 */
 	protected function addMultiValueInputTextField(&$container, $attrName, $label, $required = false, $length = null, $isTextArea = false,
-				$autoCompleteValues = null, $fieldSize = null, &$htmlIDs = null) {
+				$autoCompleteValues = null, $fieldSize = null, &$htmlIDs = null, $cssClasses = '') {
 			$values = array();
 			if (isset($this->attributes[$attrName][0])) {
 				$values = $this->attributes[$attrName];
@@ -1376,6 +1377,9 @@ abstract class baseModule {
 			for ($i = 0; $i < sizeof($values); $i++) {
 				if (!$isTextArea) {
 					$input = new htmlInputField($attrName . '_' . $i, $values[$i]);
+					if (!empty($cssClasses)) {
+						$input->setCSSClasses(array($cssClasses));
+					}
 					if (!empty($length)) {
 						$input->setFieldMaxLength($length);
 					}
@@ -1392,7 +1396,11 @@ abstract class baseModule {
 					if ($length != null) {
 						$cols = $length;
 					}
-					$subContainer->addElement(new htmlInputTextarea($attrName . '_' . $i, $values[$i], $cols, 3));
+					$textArea = new htmlInputTextarea($attrName . '_' . $i, $values[$i], $cols, 3);
+					if (!empty($cssClasses)) {
+						$textArea->setCSSClasses(array($cssClasses));
+					}
+					$subContainer->addElement($textArea);
 				}
 				if (!empty($htmlIDs)) {
 					$htmlIDs[] = $attrName . '_' . $i;
diff --git a/lam/lib/modules/yubiKeyUser.inc b/lam/lib/modules/yubiKeyUser.inc
index a307c2ff..e4481f62 100644
--- a/lam/lib/modules/yubiKeyUser.inc
+++ b/lam/lib/modules/yubiKeyUser.inc
@@ -145,7 +145,8 @@ class yubiKeyUser extends baseModule {
 			return $return;
 		}
 		if (empty($objectClass) || in_array($objectClass, $this->attributes['objectClass'])) {
-			$this->addMultiValueInputTextField($return, $attributeName, _('YubiKey ids'), false, '256', false, null, '50');
+			$htmlIds = array();
+			$this->addMultiValueInputTextField($return, $attributeName, _('YubiKey ids'), false, '12', false, null, null, $htmlIds, 'lam-prevent-enter');
 			if (!empty($objectClass)) {
 				$return->addElement(new htmlSpacer(null, '30px'), true);
 
diff --git a/lam/templates/lib/500_lam.js b/lam/templates/lib/500_lam.js
index 4e9c5e18..30d0c514 100644
--- a/lam/templates/lib/500_lam.js
+++ b/lam/templates/lib/500_lam.js
@@ -1100,6 +1100,17 @@ window.lam.html.activateLightboxes = function() {
 	});
 };
 
+/**
+ * Prevents enter key on input fields with class "lam-prevent-enter".
+ */
+window.lam.html.preventEnter = function() {
+	jQuery('.lam-prevent-enter').keypress(function (event) {
+	    if (event.keyCode === 10 || event.keyCode === 13) {
+	        event.preventDefault();
+	    }
+	});
+}
+
 window.lam.selfservice = window.lam.selfservice || {};
 
 /**
@@ -1161,4 +1172,5 @@ jQuery(document).ready(function() {
 	window.lam.tools.setInitialFocus();
 	window.lam.tools.schema.select();
 	window.lam.html.activateLightboxes();
+	window.lam.html.preventEnter();
 });