diff --git a/src/NServiceBus.Core.Tests/AssemblyScanner/When_exclusion_predicate_is_used.cs b/src/NServiceBus.Core.Tests/AssemblyScanner/When_exclusion_predicate_is_used.cs
index 3e9d939e081..6f23db3741b 100644
--- a/src/NServiceBus.Core.Tests/AssemblyScanner/When_exclusion_predicate_is_used.cs
+++ b/src/NServiceBus.Core.Tests/AssemblyScanner/When_exclusion_predicate_is_used.cs
@@ -1,5 +1,6 @@
 namespace NServiceBus.Core.Tests.AssemblyScanner
 {
+    using System;
     using System.Collections.Generic;
     using System.IO;
     using System.Linq;
@@ -15,13 +16,13 @@ public void No_files_explicitly_excluded_are_returned()
         {
             var results = new AssemblyScanner(Path.Combine(TestContext.CurrentContext.TestDirectory, "TestDlls"))
             {
-                AssembliesToSkip = new List<string>
+                AssembliesToSkip = new HashSet<string>(StringComparer.OrdinalIgnoreCase)
                     {
                         "dotNet.dll"
                     },
                 ScanAppDomainAssemblies = false
             }
-                .GetScannableAssemblies();
+            .GetScannableAssemblies();
 
             var skippedFiles = results.SkippedFiles;
             var explicitlySkippedDll = skippedFiles.FirstOrDefault(s => s.FilePath.Contains("dotNet.dll"));
diff --git a/src/NServiceBus.Core.Tests/Config/When_scanning_assemblies.cs b/src/NServiceBus.Core.Tests/Config/When_scanning_assemblies.cs
index 1f215a34faf..752dba672d7 100644
--- a/src/NServiceBus.Core.Tests/Config/When_scanning_assemblies.cs
+++ b/src/NServiceBus.Core.Tests/Config/When_scanning_assemblies.cs
@@ -1,5 +1,6 @@
 namespace NServiceBus.Core.Tests.Config
 {
+    using System;
     using System.Collections.Generic;
     using System.Linq;
     using System.Reflection;
@@ -49,7 +50,7 @@ IEnumerable<Assembly> GetAssembliesInDirectory(string path, params string[] asse
 
             if (assembliesToSkip != null)
             {
-                assemblyScanner.AssembliesToSkip = assembliesToSkip.ToList();
+                assemblyScanner.AssembliesToSkip = new HashSet<string>(assembliesToSkip.ToList(), StringComparer.OrdinalIgnoreCase);
             }
             return assemblyScanner
                 .GetScannableAssemblies()
diff --git a/src/NServiceBus.Core/Hosting/Helpers/AssemblyScanner.cs b/src/NServiceBus.Core/Hosting/Helpers/AssemblyScanner.cs
index 3d5a154918c..1f7ed635bf0 100644
--- a/src/NServiceBus.Core/Hosting/Helpers/AssemblyScanner.cs
+++ b/src/NServiceBus.Core/Hosting/Helpers/AssemblyScanner.cs
@@ -302,30 +302,9 @@ static List<FileInfo> ScanDirectoryForAssemblyFiles(string directoryToScan, bool
             return fileInfo;
         }
 
-        bool IsExcluded(string assemblyNameOrFileName)
-        {
-            foreach (var explicitlyExcludedAssembly in AssembliesToSkip)
-            {
-                if (IsMatch(explicitlyExcludedAssembly, assemblyNameOrFileName))
-                {
-                    return true;
-                }
-            }
-
-            foreach (var excludedByDefaultAssembly in DefaultAssemblyExclusions)
-            {
-                if (IsMatch(excludedByDefaultAssembly, assemblyNameOrFileName))
-                {
-                    return true;
-                }
-            }
-
-            return false;
-        }
-
-        static bool IsMatch(string expression1, string expression2)
-            => string.Equals(RemoveFileExtensionIfNecessary(expression1), RemoveFileExtensionIfNecessary(expression2), StringComparison.OrdinalIgnoreCase);
+        bool IsExcluded(string assemblyNameOrFileName) => AssembliesToSkip.Contains(assemblyNameOrFileName) || DefaultAssemblyExclusions.Contains(assemblyNameOrFileName);
 
+        // The input and output signature of this method is deliberate
         List<Type> AllowedTypes(Type[] types)
         {
             // assume the majority of types will be allowed to preallocate the list
@@ -345,15 +324,6 @@ bool IsAllowedType(Type type) =>
             Attribute.GetCustomAttribute(type, typeof(CompilerGeneratedAttribute), false) == null &&
             !TypesToSkip.Contains(type);
 
-        static string RemoveFileExtensionIfNecessary(string assemblyOrFileName)
-        {
-            if (assemblyOrFileName.EndsWith(".dll", StringComparison.OrdinalIgnoreCase) || assemblyOrFileName.EndsWith(".exe", StringComparison.OrdinalIgnoreCase))
-            {
-                return assemblyOrFileName[..^4];
-            }
-            return assemblyOrFileName;
-        }
-
         void AddTypesToResult(Assembly assembly, AssemblyScannerResults results)
         {
             try
@@ -398,15 +368,11 @@ bool ShouldScanDependencies(Assembly assembly)
                 return false;
             }
 
-            if (IsExcluded(assemblyName.Name))
-            {
-                return false;
-            }
-
-            return true;
+            // AssemblyName.Name is without the file extension
+            return !IsExcluded(assemblyName.Name);
         }
 
-        internal List<string> AssembliesToSkip = new();
+        internal HashSet<string> AssembliesToSkip = new(StringComparer.OrdinalIgnoreCase);
         internal bool ScanNestedDirectories;
         internal HashSet<Type> TypesToSkip = new();
         readonly Assembly assemblyToScan;
@@ -420,7 +386,7 @@ bool ShouldScanDependencies(Assembly assembly)
         };
 
         //TODO: delete when we make message scanning lazy #1617
-        static readonly string[] DefaultAssemblyExclusions =
+        static readonly HashSet<string> DefaultAssemblyExclusions = new(StringComparer.OrdinalIgnoreCase)
         {
             // NSB Build-Dependencies
             "nunit",
diff --git a/src/NServiceBus.Core/Hosting/Helpers/AssemblyScanningComponent.cs b/src/NServiceBus.Core/Hosting/Helpers/AssemblyScanningComponent.cs
index b1f522b5cbb..f9e78e5417f 100644
--- a/src/NServiceBus.Core/Hosting/Helpers/AssemblyScanningComponent.cs
+++ b/src/NServiceBus.Core/Hosting/Helpers/AssemblyScanningComponent.cs
@@ -2,6 +2,7 @@
 {
     using System;
     using System.Collections.Generic;
+    using System.IO;
     using System.Linq;
     using Settings;
     using Hosting.Helpers;
@@ -31,7 +32,7 @@ public static AssemblyScanningComponent Initialize(Configuration configuration,
 
             var assemblyScannerSettings = configuration.AssemblyScannerConfiguration;
 
-            assemblyScanner.AssembliesToSkip = assemblyScannerSettings.ExcludedAssemblies;
+            assemblyScanner.AssembliesToSkip = new HashSet<string>(assemblyScannerSettings.ExcludedAssemblies.Select(Path.GetFileNameWithoutExtension).ToArray(), StringComparer.OrdinalIgnoreCase);
             assemblyScanner.TypesToSkip = new HashSet<Type>(assemblyScannerSettings.ExcludedTypes);
             assemblyScanner.ScanNestedDirectories = assemblyScannerSettings.ScanAssembliesInNestedDirectories;
             assemblyScanner.ThrowExceptions = assemblyScannerSettings.ThrowExceptions;