diff --git a/Runtime/Elements/ExposedParameter.cs b/Runtime/Elements/ExposedParameter.cs
index 03d666ad..75adaa6e 100644
--- a/Runtime/Elements/ExposedParameter.cs
+++ b/Runtime/Elements/ExposedParameter.cs
@@ -68,7 +68,7 @@ void ISerializationCallbackReceiver.OnBeforeSerialize() {}
         protected virtual Settings CreateSettings() => new Settings();
 
         public virtual object value { get; set; }
-        public virtual Type GetValueType() => value.GetType();
+        public virtual Type GetValueType() => value == null ? typeof(object) : value.GetType();
 
         static Dictionary<Type, Type> exposedParameterTypeCache = new Dictionary<Type, Type>();
         internal ExposedParameter Migrate()
diff --git a/Runtime/Elements/ParameterNode.cs b/Runtime/Elements/ParameterNode.cs
index bc05b806..d86856e2 100644
--- a/Runtime/Elements/ParameterNode.cs
+++ b/Runtime/Elements/ParameterNode.cs
@@ -97,6 +97,13 @@ protected override void Process()
 			parameter = graph.GetExposedParameterFromGUID(parameterGUID);
 #endif
 
+			ClearMessages();
+			if (parameter == null)
+			{
+				AddMessage($"Parameter not found: {parameterGUID}", NodeMessageType.Error);
+				return;
+			}
+
 			if (accessor == ParameterAccessor.Get)
 				output = parameter.value;
 			else