diff --git a/M6502/M6502.Symbols/IdentifiableSection.cs b/M6502/M6502.Symbols/IdentifiableSection.cs
index f128b9c..925fd30 100644
--- a/M6502/M6502.Symbols/IdentifiableSection.cs
+++ b/M6502/M6502.Symbols/IdentifiableSection.cs
@@ -1,6 +1,5 @@
 namespace M6502.Symbols
 {
-    using System.Collections;
     using System.Diagnostics;
 
     public class IdentifiableSection : Section
diff --git a/M6502/M6502.Symbols/Section.cs b/M6502/M6502.Symbols/Section.cs
index fd65b84..07ebc6b 100644
--- a/M6502/M6502.Symbols/Section.cs
+++ b/M6502/M6502.Symbols/Section.cs
@@ -23,6 +23,7 @@
 
         protected static ReflectedSectionProperties GetSectionProperties(System.Type type)
         {
+            ArgumentNullException.ThrowIfNull(type);
             var obtained = SectionPropertiesCache.TryGetValue(type, out var properties);
             Debug.Assert(obtained, $"Section properties for {type.Name} have not been built");
             Debug.Assert(properties is not null);
diff --git a/M6502/M6502.Symbols/Symbol.cs b/M6502/M6502.Symbols/Symbol.cs
index ae2322b..e5b0051 100644
--- a/M6502/M6502.Symbols/Symbol.cs
+++ b/M6502/M6502.Symbols/Symbol.cs
@@ -1,7 +1,5 @@
 namespace M6502.Symbols
 {
-    using System.Collections.Generic;
-
     // sym id = 16, name = "solve", addrsize = absolute, size = 274, scope = 0, def = 94,ref=144+17+351,val=0xF314,seg=6,type=lab
     [Section("symbol", "Symbols")]
     public sealed class Symbol(Parser container) : NamedSection(container)
diff --git a/M6502/M6502.Test/Board.cs b/M6502/M6502.Test/Board.cs
index 139dda9..afbc4f5 100644
--- a/M6502/M6502.Test/Board.cs
+++ b/M6502/M6502.Test/Board.cs
@@ -11,7 +11,7 @@ namespace M6502.Test
     using System.Text;
     using System.Threading.Tasks;
 
-    internal class Board : Bus
+    internal sealed class Board : Bus
     {
         private readonly Configuration configuration;
         private readonly Ram ram = new(0x10000);
diff --git a/Z80/Z80.FuseTest/TestRunner.cs b/Z80/Z80.FuseTest/TestRunner.cs
index 7ade54d..ede3664 100644
--- a/Z80/Z80.FuseTest/TestRunner.cs
+++ b/Z80/Z80.FuseTest/TestRunner.cs
@@ -33,15 +33,15 @@ namespace Z80.FuseTest
         private readonly TestEvents actualEvents = new();
         private readonly EightBit.Ram ram = new(0x10000);
         private readonly EightBit.InputOutput ports = new();
-        private readonly Z80.Z80 cpu;
+        private readonly Z80 cpu;
         private readonly Disassembler disassembler;
 
         private int totalCycles;
 
         public TestRunner(Test<RegisterState> test, Result<RegisterState> result)
         {
-            this.cpu = new EightBit.Z80(this, this.ports);
-            this.disassembler = new EightBit.Disassembler(this);
+            this.cpu = new Z80(this, this.ports);
+            this.disassembler = new Disassembler(this);
             this.test = test ?? throw new ArgumentNullException(nameof(test));
             this.result = result ?? throw new ArgumentNullException(nameof(result));
 
diff --git a/Z80/Z80.Test/Board.cs b/Z80/Z80.Test/Board.cs
index 6f39176..2a3289b 100644
--- a/Z80/Z80.Test/Board.cs
+++ b/Z80/Z80.Test/Board.cs
@@ -110,6 +110,6 @@ namespace Z80.Test
 
         private void CPU_LoweredHALT(object? sender, System.EventArgs e) => this.LowerPOWER();
 
-        private void CPU_ExecutingInstruction_Debug(object? sender, System.EventArgs e) => System.Console.Error.WriteLine($"{Z80.Disassembler.State(this.CPU)}\t{this.disassembler.Disassemble(this.CPU)}");
+        private void CPU_ExecutingInstruction_Debug(object? sender, System.EventArgs e) => System.Console.Error.WriteLine($"{Disassembler.State(this.CPU)}\t{this.disassembler.Disassemble(this.CPU)}");
     }
 }