diff --git a/tools/unit-test-app/unit_test.py b/tools/unit-test-app/unit_test.py
index 3d5e4fe774..f78692667e 100755
--- a/tools/unit-test-app/unit_test.py
+++ b/tools/unit-test-app/unit_test.py
@@ -354,7 +354,7 @@ class Handler(threading.Thread):
 
         def device_wait_action(data):
             start_time = time.time()
-            expected_signal = data[0]
+            expected_signal = data[0].encode('utf-8')
             while 1:
                 if time.time() > start_time + self.timeout:
                     Utility.console_log("Timeout in device for function: %s" % self.child_case_name, color="orange")