diff --git a/src/ConductorSharp.Engine/ExecutionManager.cs b/src/ConductorSharp.Engine/ExecutionManager.cs
index fbdf2128..82fd77dc 100644
--- a/src/ConductorSharp.Engine/ExecutionManager.cs
+++ b/src/ConductorSharp.Engine/ExecutionManager.cs
@@ -68,7 +68,10 @@ public async Task StartAsync(CancellationToken cancellationToken)
 
         private Type GetInputType(Type workerType)
         {
-            var interfaces = workerType.GetInterfaces().Where(a => a.GetGenericTypeDefinition() == typeof(ITaskRequestHandler<,>)).First();
+            var interfaces = workerType
+                .GetInterfaces()
+                .Where(a => a.IsGenericType && a.GetGenericTypeDefinition() == typeof(ITaskRequestHandler<,>))
+                .First();
             var genericArguments = interfaces.GetGenericArguments();
 
             var inputType = genericArguments[0];