diff --git a/lam/docs/devel/upgrade.htm b/lam/docs/devel/upgrade.htm
index 98dc8c30..92f7cf5d 100644
--- a/lam/docs/devel/upgrade.htm
+++ b/lam/docs/devel/upgrade.htm
@@ -4,6 +4,7 @@
 
 
 
+
   
   <meta http-equiv="content-type" content="text/html; charset=ISO-8859-15"><title>Upgrade notes</title>
   
@@ -21,7 +22,13 @@ This is a list of API changes for all LAM releases.
 
 <br>
 
-<h2>3.6 -&gt; 3.7</h2>The module function <span style="font-weight: bold;">postModifyActions()</span> must return an array containing any messages to display.<br>
+<h2>3.6 -&gt; 3.7</h2>Module interface:<br>
+<ul>
+  <li><span style="font-weight: bold;">postModifyActions()</span>: Must return an array containing any messages to display</li>
+  <li><span style="font-weight: bold;">preModifyActions():</span> Changed return value from boolean to array of message arrays<br>
+  </li>
+</ul>
+
 <br>
 <h2>3.5.0 -&gt; 3.6</h2>
 LAM now supports client-side validation (required + numeric fields). See htmlInputField::setValidationRule().<br>
diff --git a/lam/lib/baseModule.inc b/lam/lib/baseModule.inc
index 23afdff6..5b2738c5 100644
--- a/lam/lib/baseModule.inc
+++ b/lam/lib/baseModule.inc
@@ -1034,14 +1034,14 @@ abstract class baseModule {
 	 * 
 	 * Calling this method requires the existence of an enclosing {@link accountContainer}.<br>
 	 * <br>
-	 * An error message should be printed if the function returns false.
+	 * The modification is aborted if an error message is returned.
 	 * 
 	 * @param boolean $newAccount new account
 	 * @param array $attributes LDAP attributes of this entry
-	 * @return boolean true, if no problems occured
+	 * @return array array which contains status messages. Each entry is an array containing the status message parameters.
 	 */
 	public function preModifyActions($newAccount, $attributes) {
-		return true;
+		return array();
 	}
 	
 	/**
diff --git a/lam/lib/modules.inc b/lam/lib/modules.inc
index 2392880b..1019261b 100644
--- a/lam/lib/modules.inc
+++ b/lam/lib/modules.inc
@@ -1636,10 +1636,13 @@ class accountContainer {
 		logNewMessage(LOG_DEBUG, 'Edit page pre/postModify attributes: ' . print_r($prePostModifyAttributes, true));
 		$preModifyOk = true;
 		foreach ($module as $singlemodule) {
-			$result = $this->module[$singlemodule]->preModifyActions($this->isNewAccount, $prePostModifyAttributes);
-			if (!$result) {
-				$preModifyOk = false;
-				break;
+			$preModifyMessages = $this->module[$singlemodule]->preModifyActions($this->isNewAccount, $prePostModifyAttributes);
+			$errors = array_merge($errors, $preModifyMessages);
+			for ($i = 0; $i < sizeof($preModifyMessages); $i++) {
+				if ($preModifyMessages[$i][0] == 'ERROR') {
+					$preModifyOk = false;
+					break;
+				}
 			}
 		}
 		if (!$preModifyOk) {