diff --git a/niprov/recording.py b/niprov/recording.py
index 7a9329e..56d9672 100644
--- a/niprov/recording.py
+++ b/niprov/recording.py
@@ -10,7 +10,9 @@ def record(command, new=None, parents=None, transient=False, args=[], kwargs={},
     """Execute a command and log it as provenance for the newly created file.
 
     Args:
-        command (list or str or callable): Commands to be executed
+        command (list or str or callable): Command to be executed. Either a 
+            string of executable system code, a list of components thereof, or 
+            a python function object. 
         new (str, optional): Override path to the new file, i.e. if it 
             cannot be parsed from the command.
         parents (list, optional): Override paths to parent files, i.e. if they 
@@ -37,7 +39,7 @@ def record(command, new=None, parents=None, transient=False, args=[], kwargs={},
                 _parents = [command[c+1]]
     else:
         transformation = command.func_name
-        code = ''
+        code = None
 
     if parents is not None:
         _parents = parents
@@ -50,7 +52,7 @@ def record(command, new=None, parents=None, transient=False, args=[], kwargs={},
         output = result.output
     else:
         command(*args, **kwargs)
-        output = ''
+        output = None
 
     return log(_new, transformation, _parents, code=code, transient=transient,
         logtext=output)
diff --git a/tests/recording.py b/tests/recording.py
index bda4943..9f278cd 100644
--- a/tests/recording.py
+++ b/tests/recording.py
@@ -62,7 +62,7 @@ def test_Python_code(self):
         self.record(myfunc, args=args, kwargs=kwargs, new='new.f', parents=['old.f'])
         myfunc.assert_called_with(*args, **kwargs)
         self.log.assert_called_with('new.f',myfunc.func_name,['old.f'], 
-            transient=False, code='', logtext='')
+            transient=False, code=None, logtext=None)
         # myfunc.func_code.co_filename