diff --git a/src/TaskIdentifier.php b/src/TaskIdentifier.php
index 2e86530..3b84f19 100644
--- a/src/TaskIdentifier.php
+++ b/src/TaskIdentifier.php
@@ -19,11 +19,11 @@ class TaskIdentifier
     public function __invoke($task)
     {
         if ($task instanceof CallbackEvent) {
-            if (is_null($task->command) && $task->description && class_exists($task->description)) {
+            if (Str::of($task->command)->isEmpty() && $task->description && class_exists($task->description)) {
                 return static::TYPE_JOB;
             }
 
-            if (is_null($task->command) && Str::is($task->description, $task->getSummaryForDisplay())) {
+            if (Str::of($task->command)->isEmpty() && Str::is($task->description, $task->getSummaryForDisplay())) {
                 return static::TYPE_CLOSURE;
             }
 
@@ -41,7 +41,7 @@ public function __invoke($task)
         }
     }
 
-    private function sanitisedCommand(string $command): string
+    private function sanitisedCommand(?string $command): string
     {
         return trim(str_replace([
             "'",