diff --git a/frappy/modules.py b/frappy/modules.py
index fa169d2..20ca29a 100644
--- a/frappy/modules.py
+++ b/frappy/modules.py
@@ -164,8 +164,9 @@ class HasAccessibles(HasProperties):
                         new_value = wfunc(self, new_value)
                         self.log.debug('write_%s(%r) returned %r', pname, value, new_value)
                         if new_value is Done:
-                            # setattr(self, pname, getattr(self, pname))
                             return getattr(self, pname)
+                        if new_value is None:
+                            new_value = value
                         setattr(self, pname, new_value)  # important! trigger the setter
                         return new_value
 
diff --git a/test/test_modules.py b/test/test_modules.py
index f801004..2f47f5b 100644
--- a/test/test_modules.py
+++ b/test/test_modules.py
@@ -727,3 +727,15 @@ def test_super_call():
 
     assert type(m).__name__ == '_Mod'
     assert type(m).__mro__[1:5] == (Mod, Base, Readable, Module)
+
+
+def test_write_method_returns_none():
+    class Mod(Module):
+        a = Parameter('', FloatRange(), readonly=False)
+
+        def write_a(self, value):
+            return None
+
+    mod = Mod('mod', LoggerStub(), {'description': ''}, ServerStub({}))
+    mod.write_a(1.5)
+    assert mod.a == 1.5