diff --git a/src/CLI/CLI.php b/src/CLI/CLI.php
index e8d5e25..8cbfa0a 100644
--- a/src/CLI/CLI.php
+++ b/src/CLI/CLI.php
@@ -87,7 +87,7 @@ class CLI
      *
      * @throws Exception
      */
-    public function __construct(Adapter $adapter = null, array $args = [])
+    public function __construct(?Adapter $adapter = null, array $args = [])
     {
         if (\php_sapi_name() !== 'cli') {
             throw new Exception('CLI tasks can only work from the command line');
diff --git a/src/CLI/Console.php b/src/CLI/Console.php
index 8014859..b025b52 100644
--- a/src/CLI/Console.php
+++ b/src/CLI/Console.php
@@ -130,7 +130,7 @@ public static function exit(int $status = 0): void
      * @param  int  $timeout
      * @return int
      */
-    public static function execute(array|string $cmd, string $input, string &$output, int $timeout = -1, callable $onProgress = null): int
+    public static function execute(array|string $cmd, string $input, string &$output, int $timeout = -1, ?callable $onProgress = null): int
     {
         // If the $cmd is passed as string, it will be wrapped into a subshell by \proc_open
         // Forward stdout and exit codes from the subshell.
@@ -216,7 +216,7 @@ public static function isInteractive(): bool
      *
      * @throws \Exception
      */
-    public static function loop(callable $callback, int $sleep = 1 /* seconds */, int $delay = 0 /* seconds */, callable $onError = null): void
+    public static function loop(callable $callback, int $sleep = 1 /* seconds */, int $delay = 0 /* seconds */, ?callable $onError = null): void
     {
         gc_enable();