diff --git a/apertis_tests_lib/bluez.py b/apertis_tests_lib/bluez.py
index 1afde347dfc748c2fe1de9cd48eb9b2687f7501b..0631293f2a157194cbfdae19cbcba7004944a5b2 100644
--- a/apertis_tests_lib/bluez.py
+++ b/apertis_tests_lib/bluez.py
@@ -324,7 +324,7 @@ def adapters_ensure_powered(adapters, result_func):
         }, inner_result_func)
 
 
-def adapters_make_pairable(adapters, result_func):
+def adapters_make_pairable(adapters, result_func=None):
     assert(len(adapters) > 0)
     remaining = set(adapters)
 
@@ -333,7 +333,7 @@ def adapters_make_pairable(adapters, result_func):
 
         print('Adapter ‘%s’ is pairable' % obj.object_path)
         remaining.remove(obj)
-        if len(remaining) == 0:
+        if not remaining and result_func:
             result_func()
 
     for adapter in adapters:
@@ -345,7 +345,7 @@ def adapters_make_pairable(adapters, result_func):
         }, inner_result_func)
 
 
-def adapters_make_discoverable(adapters, result_func):
+def adapters_make_discoverable(adapters, result_func=None):
     assert(len(adapters) > 0)
     remaining = set(adapters)
 
@@ -354,7 +354,7 @@ def adapters_make_discoverable(adapters, result_func):
 
         print('Adapter ‘%s’ is discoverable' % obj.object_path)
         remaining.remove(obj)
-        if len(remaining) == 0:
+        if not remaining and result_func:
             result_func()
 
     for adapter in adapters: