diff --git a/src/Directory.Build.targets b/src/Directory.Build.targets
index 1c239dc61..347ab888d 100644
--- a/src/Directory.Build.targets
+++ b/src/Directory.Build.targets
@@ -10,4 +10,8 @@
   <PropertyGroup Condition="$(TargetFramework.StartsWith('netstandard')) or $(TargetFramework.StartsWith('net6')) or $(TargetFramework.StartsWith('net7')) or $(TargetFramework.StartsWith('net8')) or $(TargetFramework.StartsWith('net9')) or $(TargetFramework.StartsWith('net10'))">
     <DefineConstants>$(DefineConstants);NETSTANDARD;P_LINQ;SUPPORTS_BINDINGLIST;SUPPORTS_ASYNC_DISPOSABLE</DefineConstants>
   </PropertyGroup>
+
+  <PropertyGroup Condition="$(TargetFramework.StartsWith('netstandard2.1')) or $(TargetFramework.StartsWith('netcoreapp3')) or $(TargetFramework.StartsWith('net5')) or $(TargetFramework.StartsWith('net6')) or $(TargetFramework.StartsWith('net7')) or $(TargetFramework.StartsWith('net8')) or $(TargetFramework.StartsWith('net9')) or $(TargetFramework.StartsWith('net10'))">
+    <DefineConstants>$(DefineConstants);SUPPORTS_DICTIONARY_MUTATION_DURING_ENUMERATION</DefineConstants>
+  </PropertyGroup>
 </Project>
diff --git a/src/DynamicData/Cache/Internal/Filter.Dynamic.cs b/src/DynamicData/Cache/Internal/Filter.Dynamic.cs
index 9727c04a3..350ae272b 100644
--- a/src/DynamicData/Cache/Internal/Filter.Dynamic.cs
+++ b/src/DynamicData/Cache/Internal/Filter.Dynamic.cs
@@ -378,7 +378,11 @@ private void OnSourceNext(IChangeSet<TObject, TKey> upstreamChanges)
 
             private void ReFilter(TState predicateState)
             {
+                #if SUPPORTS_DICTIONARY_MUTATION_DURING_ENUMERATION
                 foreach (var key in _itemStatesByKey.Keys)
+                #else
+                foreach (var key in _itemStatesByKey.Keys.ToArray())
+                #endif
                 {
                     var itemState = _itemStatesByKey[key];