diff --git a/ChangeLog b/ChangeLog
index 60521f04c81..e499c5b4e1c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -31,7 +31,8 @@ WARNING: Following changes may create regression for some external modules, but
 Dolibarr better:
 - Removed hoo supplierorderdao into supplier order creation. This is a business event, so we must use the 
   trigger ORDER_SUPPLIER_CREATE instead.
-
+- printLeftBlock is now compliant with hook development rules. It is an "addreplace" hook so you must 
+return content by doing ->resprints='mycontent' and not by doing return 'mycontent'  
 
 
 ***** ChangeLog for 3.7 compared to 3.6.* *****
diff --git a/htdocs/main.inc.php b/htdocs/main.inc.php
index 1855ff9b42e..edf86c52853 100644
--- a/htdocs/main.inc.php
+++ b/htdocs/main.inc.php
@@ -1686,8 +1686,8 @@ function left_menu($menu_array_before, $helppagename='', $moresearchform='', $me
 
 	    // Execute hook printLeftBlock
 	    $parameters=array();
-	    $leftblock=$hookmanager->executeHooks('printLeftBlock',$parameters);    // Note that $action and $object may have been modified by some hooks
-	    print $leftblock;
+	    $reshook=$hookmanager->executeHooks('printLeftBlock',$parameters);    // Note that $action and $object may have been modified by some hooks
+	    print $hookmanager->resPrint;
 
 	    if (empty($conf->dol_use_jmobile) && ! empty($conf->use_javascript_ajax) && ! empty($conf->global->MAIN_MENU_USE_JQUERY_LAYOUT)) print '</div> <!-- End left layout -->'."\n";
 	    else print '</div> <!-- end id-left -->';	// End div id="id-left"