diff --git a/program/include/rcube_shared.inc b/program/include/rcube_shared.inc
index e740aeaa3..af5eb1fda 100644
--- a/program/include/rcube_shared.inc
+++ b/program/include/rcube_shared.inc
@@ -210,7 +210,7 @@ function array2js($arr, $type='')
 function in_array_nocase($needle, $haystack)
 {
   foreach ($haystack as $value)
-    if (strtolower($needle)===strtolower($value))
+    if (rc_strtolower($needle)===rc_strtolower($value))
       return true;
   
   return false;
diff --git a/program/steps/mail/compose.inc b/program/steps/mail/compose.inc
index efc979023..df6f1ffae 100644
--- a/program/steps/mail/compose.inc
+++ b/program/steps/mail/compose.inc
@@ -219,7 +219,7 @@ function rcmail_compose_headers($attrib)
         if (!empty($addr_part['mailto'])
 	    && !in_array($addr_part['mailto'], $sa_recipients)
 	    && (!$MESSAGE->compose_from
-		|| !in_array($addr_part['mailto'], $MESSAGE->compose_from)
+		|| !in_array_nocase($addr_part['mailto'], $MESSAGE->compose_from)
 		|| count($to_addresses)==1)) // allow reply to yourself
         {
           $fvalue .= (strlen($fvalue) ? ', ':'').$addr_part['string'];