diff --git a/library/Pdfexport/ShellCommand.php b/library/Pdfexport/ShellCommand.php
index c669773..1fa944d 100644
--- a/library/Pdfexport/ShellCommand.php
+++ b/library/Pdfexport/ShellCommand.php
@@ -102,8 +102,8 @@ public function execute()
         $stdout = '';
         $stderr = '';
 
-        stream_set_blocking($namedpipes->stdout, 0); // non-blocking
-        stream_set_blocking($namedpipes->stderr, 0);
+        stream_set_blocking($namedpipes->stdout, false); // non-blocking
+        stream_set_blocking($namedpipes->stderr, false);
 
         while (stream_select($read, $write, $except, 0, 20000) !== false) {
             foreach ($read as $pipe) {