diff --git a/loopy/compiled.py b/loopy/compiled.py
index 2a1f5fb8123c16cbb27ddc34bebd08736a8a09b5..7156f3c1ad8098cfcf3295bb5e5576770d07f4f5 100644
--- a/loopy/compiled.py
+++ b/loopy/compiled.py
@@ -625,8 +625,8 @@ def generate_invoker(kernel, impl_arg_info, flags):
         out_args = [arg
                 for arg in impl_arg_info
                 if arg.base_name in kernel.get_written_variables()]
-        if not out_args:
-            gen("return _lpy_evt, (%s)"
+        if out_args:
+            gen("return _lpy_evt, (%s,)"
                     % ", ".join(arg.name for arg in out_args))
         else:
             gen("return _lpy_evt, ()")