diff --git a/examples/cpuinfo/app.py b/examples/cpuinfo/app.py
index c06ca9ab9..75607657b 100644
--- a/examples/cpuinfo/app.py
+++ b/examples/cpuinfo/app.py
@@ -140,7 +140,7 @@ def collect_cpu_samples():
                     combined_data = combined_data[:, -MAX_SAMPLES:]
                 cpu_history.set(combined_data)
 
-    @reactive.Effect(priority=100)
+    @reactive.effect(priority=100)
     @reactive.event(input.reset)
     def reset_history():
         cpu_history.set(None)
diff --git a/shiny/reactive/_reactives.py b/shiny/reactive/_reactives.py
index 54c855579..59b9c7e51 100644
--- a/shiny/reactive/_reactives.py
+++ b/shiny/reactive/_reactives.py
@@ -480,6 +480,14 @@ def __init__(
         self.__name__ = fn.__name__
         self.__doc__ = fn.__doc__
 
+        from ..render.renderer import RendererBase
+
+        if isinstance(fn, RendererBase):
+            raise TypeError(
+                "`@reactive.effect` can not be combined with `@render.xx`.\n"
+                + "Please remove your call of `@reactive.effect`."
+            )
+
         # The EffectAsync subclass will pass in an async function, but it tells the
         # static type checker that it's synchronous. wrap_async() is smart -- if is
         # passed an async function, it will not change it.
diff --git a/tests/pytest/test_renderer.py b/tests/pytest/test_renderer.py
index 18af6a093..15a5417a5 100644
--- a/tests/pytest/test_renderer.py
+++ b/tests/pytest/test_renderer.py
@@ -4,6 +4,7 @@
 
 import pytest
 
+from shiny import reactive, render
 from shiny.render.renderer import Renderer, ValueFn
 
 
@@ -53,3 +54,12 @@ def txt4() -> str:
     assert val == "42 42"
     val = await txt4.render()
     assert val == "42 42 42 42"
+
+
+def test_effect():
+    with pytest.raises(TypeError):
+
+        @reactive.effect  # pyright: ignore[reportGeneralTypeIssues]
+        @render.text
+        def my_output():
+            return "42"