diff --git a/src/aiida/orm/nodes/data/code/installed.py b/src/aiida/orm/nodes/data/code/installed.py
index ad05fd45b0..01009b2210 100644
--- a/src/aiida/orm/nodes/data/code/installed.py
+++ b/src/aiida/orm/nodes/data/code/installed.py
@@ -140,7 +140,7 @@ def validate_filepath_executable(self):
                     if file_exists:
                         mode = transport.get_mode(str(self.filepath_executable))
                         # check if execute but is set
-                        user_has_execute = format(mode, "b")[6] == '1'
+                        user_has_execute = format(mode, 'b')[6] == '1'
 
         except Exception as exception:
             raise exceptions.ValidationError(