diff --git a/contrib/pylightning/lightning/plugin.py b/contrib/pylightning/lightning/plugin.py
index d7b52dcd8..3da175d70 100644
--- a/contrib/pylightning/lightning/plugin.py
+++ b/contrib/pylightning/lightning/plugin.py
@@ -1,6 +1,6 @@
 from collections import OrderedDict
 from enum import Enum
-from lightning import LightningRpc
+from lightning import LightningRpc, Millisatoshi
 from threading import RLock
 
 import inspect
@@ -293,7 +293,11 @@ class Plugin(object):
         if isinstance(params, dict):
             for k, v in params.items():
                 if k in arguments:
-                    arguments[k] = v
+                    # Explicitly (try to) interpret as Millisatoshi if annotated
+                    if func.__annotations__.get(k) == Millisatoshi:
+                        arguments[k] = Millisatoshi(v)
+                    else:
+                        arguments[k] = v
                 else:
                     kwargs[k] = v
         else:
@@ -305,7 +309,10 @@ class Plugin(object):
 
                 if pos < len(params):
                     # Apply positional args if we have them
-                    arguments[k] = params[pos]
+                    if func.__annotations__.get(k) == Millisatoshi:
+                        arguments[k] = Millisatoshi(params[pos])
+                    else:
+                        arguments[k] = params[pos]
                 elif sig.parameters[k].default is inspect.Signature.empty:
                     # This is a positional arg with no value passed
                     raise TypeError("Missing required parameter: %s" % sig.parameters[k])
@@ -406,6 +413,8 @@ class Plugin(object):
         Returns the last partial message that was not complete yet.
         """
         for payload in msgs[:-1]:
+            # Note that we use function annotations to do Millisatoshi conversions
+            # in _exec_func, so we don't use LightningJSONDecoder here.
             request = self._parse_request(json.loads(payload))
 
             # If this has an 'id'-field, it's a request and returns a
diff --git a/tests/test_plugin.py b/tests/test_plugin.py
index 5df0c47bb..5a5331dbf 100644
--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -34,7 +34,6 @@ def test_option_passthrough(node_factory):
     n.stop()
 
 
-@pytest.mark.xfail(strict=True)
 def test_millisatoshi_passthrough(node_factory):
     """ Ensure that Millisatoshi arguments and return work.
     """