diff --git a/src/GO/Scheduler.php b/src/GO/Scheduler.php
index 53eb07a..5e2e2b0 100644
--- a/src/GO/Scheduler.php
+++ b/src/GO/Scheduler.php
@@ -119,6 +119,10 @@ public function call(callable $fn, $args = [], $id = null)
      */
     public function php($script, $bin = null, $args = [], $id = null)
     {
+        if (! is_string($script) || ! file_exists($script)) {
+            throw new InvalidArgumentException('The script should be a valid path to a file.');
+        }
+
         $bin = $bin !== null && is_string($bin) && file_exists($bin) ?
             $bin : (PHP_BINARY === '' ? '/usr/bin/php' : PHP_BINARY);
 
diff --git a/tests/GO/SchedulerTest.php b/tests/GO/SchedulerTest.php
index 731cfd0..70e2398 100644
--- a/tests/GO/SchedulerTest.php
+++ b/tests/GO/SchedulerTest.php
@@ -30,6 +30,30 @@ public function testShouldQueueAPhpScript()
         $this->assertEquals(count($scheduler->getQueuedJobs()), 1);
     }
 
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testShouldThrowExceptionIfScriptIsNotAString()
+    {
+        $scheduler = new Scheduler();
+        $scheduler->php(function () {
+            return false;
+        });
+
+        $scheduler->run();
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testShouldThrowExceptionIfScriptPathIsInvalid()
+    {
+        $scheduler = new Scheduler();
+        $scheduler->php('someInvalidPathToAScript');
+
+        $scheduler->run();
+    }
+
     public function testShouldQueueAShellCommand()
     {
         $scheduler = new Scheduler();