Index: src/drv_imap.c
===================================================================
--- src/drv_imap.c.orig
+++ src/drv_imap.c
@@ -1229,7 +1229,7 @@
 				_exit( 127 );
 			close( a[0] );
 			close( a[1] );
-			execl( "/bin/sh", "sh", "-c", srvc->tunnel, 0 );
+			execl( "/bin/sh", "sh", "-c", srvc->tunnel, NULL );
 			_exit( 127 );
 		}