--- a/testing/mozbase/mozprocess/tests/test_output.py
+++ b/testing/mozbase/mozprocess/tests/test_output.py
@@ -29,17 +29,18 @@ class ProcTestOutput(proctest.ProcTest):
         p.wait()
 
         self.determine_status(p, False, ())
 
     def test_process_output_nonewline(self):
         """
         Process is started, outputs data with no newline
         """
-        p = processhandler.ProcessHandler([self.python, "scripts", "procnonewline.py"],
+        p = processhandler.ProcessHandler([self.python,
+                                           os.path.join("scripts", "procnonewline.py")],
                                           cwd=here)
 
         p.run()
         p.processOutput(timeout=5)
         p.wait()
 
         self.determine_status(p, False, ())