diff --git a/wlauto/common/android/device.py b/wlauto/common/android/device.py
index 47158b73..f4257268 100644
--- a/wlauto/common/android/device.py
+++ b/wlauto/common/android/device.py
@@ -475,8 +475,8 @@ class AndroidDevice(BaseLinuxDevice):  # pylint: disable=W0223
 
     def get_pids_of(self, process_name):
         """Returns a list of PIDs of all processes with the specified name."""
-        result = self.execute('ps | {} grep {}'.format(self.busybox, process_name),
-                              check_exit_code=False).strip()
+        result = (self.execute('ps | {} grep {}'.format(self.busybox, process_name),
+                               check_exit_code=False) or '').strip()
         if result and 'not found' not in result:
             return [int(x.split()[1]) for x in result.split('\n')]
         else: