diff --git a/cmdline.c b/cmdline.c
index bc89020..11524d3 100644
--- a/cmdline.c
+++ b/cmdline.c
@@ -631,7 +631,7 @@ int cmdline_parser( int argc, char * const *argv, struct gengetopt_args_info *ar
 			message( "Out of memory\n" );
 			exit(1);
 		}
-		snprintf( proxy_arg_fmt, sizeof(proxy_arg_fmt), "%%%zu[^:]:%%5u", proxy_arg_len - 1 );
+		snprintf( proxy_arg_fmt, sizeof(proxy_arg_fmt), "%%%zu[^][:]:%%5u", proxy_arg_len - 1 );
 		r = sscanf( args_info->proxy_arg, proxy_arg_fmt, phost, &pport );
 		if ( r != 2 ) {
 			/* try bracket-enclosed IPv6 literal */