diff --git a/hippolyzer/lib/proxy/commands.py b/hippolyzer/lib/proxy/commands.py
index 6662225..d32de70 100644
--- a/hippolyzer/lib/proxy/commands.py
+++ b/hippolyzer/lib/proxy/commands.py
@@ -65,13 +65,13 @@ def handle_command(command_name: Optional[str] = None, /, *, lifetime: Optional[
                 # Greedy, takes the rest of the message
                 if param.sep is None:
                     param_val = message
-                    message = None
+                    message = ""
                 else:
                     message = message.lstrip(param.sep)
                     if not message:
-                        if param.optional:
-                            break
-                        raise KeyError(f"Missing parameter {param_name}")
+                        if not param.optional:
+                            raise KeyError(f"Missing parameter {param_name}")
+                        continue
                     param_val, _, message = message.partition(param.sep)  # type: ignore
 
                 param_vals[param_name] = param.parser(param_val)
diff --git a/tests/proxy/test_commands.py b/tests/proxy/test_commands.py
index b6c2d90..e5914c5 100644
--- a/tests/proxy/test_commands.py
+++ b/tests/proxy/test_commands.py
@@ -26,7 +26,13 @@ class ExampleCommandHandler:
         y=str,
     )
     async def own_name(self, _session, _region, y):
-        self.bar = y
+        pass
+
+    @handle_command(
+        x=Parameter(str, optional=True),
+    )
+    async def optional(self, _session, _region, x=42):
+        self.bar = x
 
 
 class TestCommandHandlers(unittest.IsolatedAsyncioTestCase):
@@ -47,6 +53,17 @@ class TestCommandHandlers(unittest.IsolatedAsyncioTestCase):
     async def test_own_name(self):
         self.assertEqual(self.handler.own_name.command.name, "own_name")
 
+    async def test_missing_param(self):
+        with self.assertRaises(KeyError):
+            await self.handler.foo(None, None, "")
+
+    async def test_optional_param(self):
+        await self.handler.optional(None, None, "foo")  # type: ignore
+        self.assertEqual(self.handler.bar, "foo")
+        await self.handler.optional(None, None, "")  # type: ignore
+        # Should have picked up the default value
+        self.assertEqual(self.handler.bar, 42)
+
     async def test_bad_command(self):
         with self.assertRaises(ValueError):
             class _BadCommandHandler: