diff --git a/program/lib/imap.inc b/program/lib/imap.inc
index a8f318c20..b7c0b69eb 100644
--- a/program/lib/imap.inc
+++ b/program/lib/imap.inc
@@ -389,7 +389,7 @@ function iil_C_GetCapability(&$conn, $name)
 	return false;
 }
 
-function iil_C_ClearCapability($conn)
+function iil_C_ClearCapability(&$conn)
 {
 	$conn->capability = array();
 	$conn->capability_readed = false;