diff --git a/light9/effect/effecteval.py b/light9/effect/effecteval.py
--- a/light9/effect/effecteval.py
+++ b/light9/effect/effecteval.py
@@ -77,6 +77,7 @@ class EffectEval2:
     uri: EffectUri
 
     effectFunction: Optional[URIRef] = None
+    isEffect = False
 
     def __post_init__(self):
         self.graph.addHandler(self._compile)
@@ -84,7 +85,9 @@ class EffectEval2:
 
     def _compile(self):
         if not self.graph.contains((self.uri, RDF.type, L9['Effect'])):
-            raise ValueError(f'{self.uri} not an :Effect')
+            self.isEffect = False
+            return
+        self.isEffect = True
 
         self.function = effect_scale
         devs = []
@@ -96,6 +99,8 @@ class EffectEval2:
         self.devs = DeviceSettings(self.graph, devs)
 
     def compute(self, inputs: EffectSettings) -> DeviceSettings:
+        if not self.isEffect:
+            return DeviceSettings(self.graph, [])
 
         s = 0
         for e, ea, v in inputs.asList():