diff --git a/build/build.props b/build/build.props
index 3dddd29..03764a5 100644
--- a/build/build.props
+++ b/build/build.props
@@ -6,7 +6,7 @@
     <PackageLicenseFile>LICENSE.txt</PackageLicenseFile>
     <PackageProjectUrl>https://github.com/jspuij/Cortex.Net</PackageProjectUrl>
     <DisableFody>true</DisableFody>
-    <Version>0.1.0-preview5</Version>
+    <Version>0.1.0-preview7</Version>
     <NeutralLanguage>en-US</NeutralLanguage>
 </PropertyGroup>
 
diff --git a/src/Cortex.Net/Core/DerivationExtensions.cs b/src/Cortex.Net/Core/DerivationExtensions.cs
index 80fe85e..cacc10f 100644
--- a/src/Cortex.Net/Core/DerivationExtensions.cs
+++ b/src/Cortex.Net/Core/DerivationExtensions.cs
@@ -195,7 +195,7 @@ private static void BindDependencies(this IDerivation derivation)
 
             var lowestNewObservingDerivationState = DerivationState.UpToDate;
 
-            foreach (var dependency in derivation.NewObserving.ToList())
+            foreach (var dependency in derivation.NewObserving)
             {
                 if (dependency is IDerivation)
                 {
@@ -203,7 +203,7 @@ private static void BindDependencies(this IDerivation derivation)
                 }
             }
 
-            foreach (var dependency in derivation.Observing.ToList())
+            foreach (var dependency in derivation.Observing)
             {
                 if (!derivation.NewObserving.Contains(dependency))
                 {