diff --git a/src/Stryker.Core/Stryker.Core/Initialisation/InputFileResolver.cs b/src/Stryker.Core/Stryker.Core/Initialisation/InputFileResolver.cs
index f2b249c7a..9410a2e22 100644
--- a/src/Stryker.Core/Stryker.Core/Initialisation/InputFileResolver.cs
+++ b/src/Stryker.Core/Stryker.Core/Initialisation/InputFileResolver.cs
@@ -542,20 +542,20 @@ private static StringBuilder BuildReferenceChoice(IEnumerable<string> projectRef
 
     private sealed class DynamicEnumerableQueue<T>
     {
-        private readonly Queue<T> _queue;
-        private readonly HashSet<T> _cache;
+        private readonly ConcurrentQueue<T> _queue;
+        private readonly ConcurrentDictionary<T, bool> _cache;
 
         public DynamicEnumerableQueue(IEnumerable<T> init)
         {
-            _cache = [.. init];
-            _queue = new Queue<T>(_cache);
+            _cache = new(init.ToDictionary(x => x, x => true));
+            _queue = new (_cache.Keys);
         }
 
-        public bool Empty => _queue.Count == 0;
+        public bool Empty => _queue.IsEmpty;
 
         public void Add(T entry)
         {
-            if (!_cache.Add(entry))
+            if (!_cache.TryAdd(entry, true))
             {
                 return;
             }
@@ -566,7 +566,10 @@ public IEnumerable<T> Consume()
         {
             while (_queue.Count > 0)
             {
-                yield return _queue.Dequeue();
+                if (_queue.TryDequeue(out var entry))
+                {
+                    yield return entry;
+                }
             }
         }
     }
diff --git a/src/Stryker.Core/Stryker.Core/InjectedHelpers/MutantControl.cs b/src/Stryker.Core/Stryker.Core/InjectedHelpers/MutantControl.cs
index 1eed3837a..557d69015 100644
--- a/src/Stryker.Core/Stryker.Core/InjectedHelpers/MutantControl.cs
+++ b/src/Stryker.Core/Stryker.Core/InjectedHelpers/MutantControl.cs
@@ -50,14 +50,21 @@ public static bool IsActive(int id)
 #pragma warning disable CS8600
                 // get the environment variable storign the mutation id
                 string environmentVariableName = System.Environment.GetEnvironmentVariable("STRYKER_CONTROL_VAR");
-                string environmentVariable = System.Environment.GetEnvironmentVariable(environmentVariableName);
-                if (string.IsNullOrEmpty(environmentVariable))
+                if (environmentVariableName != null)
                 {
-                    ActiveMutant = -1;
+                    string environmentVariable = System.Environment.GetEnvironmentVariable(environmentVariableName);
+                    if (string.IsNullOrEmpty(environmentVariable))
+                    {
+                        ActiveMutant = -1;
+                    }
+                    else
+                    {
+                        ActiveMutant = int.Parse(environmentVariable);
+                    }
                 }
                 else
                 {
-                    ActiveMutant = int.Parse(environmentVariable);
+                    ActiveMutant = -1;
                 }
             }
 
diff --git a/src/Stryker.Core/Stryker.Core/libman.json b/src/Stryker.Core/Stryker.Core/libman.json
index 91bcbe968..8f0314660 100644
--- a/src/Stryker.Core/Stryker.Core/libman.json
+++ b/src/Stryker.Core/Stryker.Core/libman.json
@@ -3,7 +3,7 @@
   "defaultProvider": "jsdelivr",
   "libraries": [
     {
-      "library": "mutation-testing-elements@3.3.0",
+      "library": "mutation-testing-elements@3.4.0",
       "files": [
         "dist/mutation-test-elements.js"
       ],