diff --git a/src/BackgroundProcess.php b/src/BackgroundProcess.php
index 599265c..052ba95 100755
--- a/src/BackgroundProcess.php
+++ b/src/BackgroundProcess.php
@@ -94,8 +94,9 @@ public function isRunning()
                                  'systems, such as Unix, Linux or Mac OS X. You are running "%s".');
 
         try {
-            $result = shell_exec(sprintf('ps %d 2>&1', $this->pid));
-            if (count(preg_split("/\n/", $result)) > 2 && !preg_match('/ERROR: Process ID out of range/', $result)) {
+            $result = shell_exec("ps -ef | awk '{print $1}'");
+            $pidArray = explode(PHP_EOL, $result);
+            if (in_array($this->pid,$pidArray) && !preg_match('/ERROR: Process ID out of range/', $result)) {
                 return true;
             }
         } catch (Exception $e) {