diff --git a/src/EcsRunner.cs b/src/EcsRunner.cs
index 46c8719..70a7109 100644
--- a/src/EcsRunner.cs
+++ b/src/EcsRunner.cs
@@ -61,10 +61,13 @@ namespace DCFApixels.DragonECS
             Type runnerBaseType = typeof(EcsRunner<>);
 
             List<Type> runnerHandlerTypes = new List<Type>();
-            runnerHandlerTypes = Assembly.GetAssembly(runnerBaseType)
-                .GetTypes()
-                .Where(type => type.BaseType != null && type.BaseType.IsGenericType && runnerBaseType == type.BaseType.GetGenericTypeDefinition())
-                .ToList();
+
+            foreach (var assembly in AppDomain.CurrentDomain.GetAssemblies())
+            {
+                runnerHandlerTypes.AddRange(
+                    assembly.GetTypes()
+                    .Where(type => type.BaseType != null && type.BaseType.IsGenericType && runnerBaseType == type.BaseType.GetGenericTypeDefinition()));
+            }
 
 #if DEBUG || !DRAGONECS_NO_SANITIZE_CHECKS
             for (int i = 0; i < runnerHandlerTypes.Count; i++)
diff --git a/src/EcsSystems.cs b/src/EcsSystems.cs
index 73bb6af..5c43b59 100644
--- a/src/EcsSystems.cs
+++ b/src/EcsSystems.cs
@@ -190,7 +190,10 @@ namespace DCFApixels.DragonECS
                 }
                 foreach (var item in _blockExecutionOrder)
                 {
-                    result.AddRange(_systems[item]);
+                    if(_systems.TryGetValue(item, out var list))
+                    {
+                        result.AddRange(list);
+                    }
                 }
 
                 return new EcsSystems(result.ToArray());