diff --git a/NESDecompiler.CLI/Program.cs b/NESDecompiler.CLI/Program.cs
index 9f2c13c..214deac 100644
--- a/NESDecompiler.CLI/Program.cs
+++ b/NESDecompiler.CLI/Program.cs
@@ -165,7 +165,7 @@ namespace NESDecompiler.CLI
             writer.WriteLine(" */");
             writer.WriteLine();
 
-            string guardName = Path.GetFileNameWithoutExtension(decompiler.ROMInfo.RawData[0].ToString()).ToUpper() + "_H";
+            string guardName = Path.GetFileNameWithoutExtension(decompiler.ROMInfo.RawData![0].ToString()).ToUpper() + "_H";
             writer.WriteLine($"#ifndef {guardName}");
             writer.WriteLine($"#define {guardName}");
             writer.WriteLine();
diff --git a/NESDecompiler.Core/Decompilation/Decompiler.cs b/NESDecompiler.Core/Decompilation/Decompiler.cs
index 9de2f6e..b3c1ba2 100644
--- a/NESDecompiler.Core/Decompilation/Decompiler.cs
+++ b/NESDecompiler.Core/Decompilation/Decompiler.cs
@@ -1026,7 +1026,7 @@ namespace NESDecompiler.Core.Decompilation
         {
             // Process LDA, LDX, LDY
             string register = instruction.Info.Mnemonic.Substring(2);
-            string variableName = GetVariableName(instruction);
+            string? variableName = GetVariableName(instruction);
 
             if (variableName != null)
             {
@@ -1046,7 +1046,7 @@ namespace NESDecompiler.Core.Decompilation
         {
             // Process STA, STX, STY
             string register = instruction.Info.Mnemonic.Substring(2);
-            string variableName = GetVariableName(instruction);
+            string? variableName = GetVariableName(instruction);
 
             if (variableName != null)
             {
@@ -1314,7 +1314,7 @@ namespace NESDecompiler.Core.Decompilation
         private void GenerateArithmeticCode(DisassembledInstruction instruction, StringBuilder sb)
         {
             // Handle arithmetic operations: ADC, SBC
-            string operand = GetOperandString(instruction);
+            string? operand = GetOperandString(instruction);
             if (operand == null)
                 return;
 
@@ -1359,7 +1359,7 @@ namespace NESDecompiler.Core.Decompilation
         private void GenerateIncrementCode(DisassembledInstruction instruction, StringBuilder sb)
         {
             // Handle increment operations: INC, INX, INY
-            string operand = GetOperandString(instruction);
+            string? operand = GetOperandString(instruction);
 
             switch (instruction.Info.Mnemonic)
             {
@@ -1393,7 +1393,7 @@ namespace NESDecompiler.Core.Decompilation
         private void GenerateDecrementCode(DisassembledInstruction instruction, StringBuilder sb)
         {
             // Handle decrement operations: DEC, DEX, DEY
-            string operand = GetOperandString(instruction);
+            string? operand = GetOperandString(instruction);
 
             switch (instruction.Info.Mnemonic)
             {
@@ -1427,7 +1427,7 @@ namespace NESDecompiler.Core.Decompilation
         private void GenerateShiftCode(DisassembledInstruction instruction, StringBuilder sb)
         {
             // Handle shift operations: ASL, LSR, ROL, ROR
-            string operand;
+            string? operand;
 
             if (instruction.Info.AddressingMode == AddressingMode.Accumulator)
             {
@@ -1489,7 +1489,7 @@ namespace NESDecompiler.Core.Decompilation
         private void GenerateLogicCode(DisassembledInstruction instruction, StringBuilder sb)
         {
             // Handle logic operations: AND, ORA, EOR, BIT
-            string operand = GetOperandString(instruction);
+            string? operand = GetOperandString(instruction);
             if (operand == null)
                 return;
 
@@ -1533,7 +1533,7 @@ namespace NESDecompiler.Core.Decompilation
         private void GenerateCompareCode(DisassembledInstruction instruction, StringBuilder sb)
         {
             // Handle compare operations: CMP, CPX, CPY
-            string operand = GetOperandString(instruction);
+            string? operand = GetOperandString(instruction);
             if (operand == null)
                 return;
 
@@ -1710,7 +1710,7 @@ namespace NESDecompiler.Core.Decompilation
             }
         }
 
-        private string GetOperandString(DisassembledInstruction instruction)
+        private string? GetOperandString(DisassembledInstruction instruction)
         {
             if (instruction.Info.AddressingMode == AddressingMode.Immediate)
             {
diff --git a/NESDecompiler.Core/Disassembly/Disassembler.cs b/NESDecompiler.Core/Disassembly/Disassembler.cs
index 4e22e5d..05f9d8e 100644
--- a/NESDecompiler.Core/Disassembly/Disassembler.cs
+++ b/NESDecompiler.Core/Disassembly/Disassembler.cs
@@ -25,17 +25,17 @@ namespace NESDecompiler.Core.Disassembly
         /// <summary>
         /// Information about this instruction's opcode
         /// </summary>
-        public InstructionInfo Info { get; set; }
+        public required InstructionInfo Info { get; init; }
 
         /// <summary>
         /// The raw bytes of this instruction (including operands)
         /// </summary>
-        public byte[] Bytes { get; set; }
+        public byte[]? Bytes { get; set; }
 
         /// <summary>
         /// The operand bytes of this instruction
         /// </summary>
-        public byte[] Operands => Bytes.Length > 1 ? Bytes[1..] : Array.Empty<byte>();
+        public byte[] Operands => Bytes!.Length > 1 ? Bytes[1..] : Array.Empty<byte>();
 
         /// <summary>
         /// The target address for branch and jump instructions
@@ -85,7 +85,7 @@ namespace NESDecompiler.Core.Disassembly
             }
 
             sb.Append($"{CPUAddress:X4}  ");
-            foreach (var b in Bytes)
+            foreach (var b in Bytes!)
             {
                 sb.Append($"{b:X2} ");
             }
@@ -398,7 +398,7 @@ namespace NESDecompiler.Core.Disassembly
                     if (instruction.TargetAddress.HasValue)
                     {
                         ushort target = instruction.TargetAddress.Value;
-                        if (labels.TryGetValue(target, out string label))
+                        if (labels.TryGetValue(target, out string? label))
                         {
                             instruction.Comment = $"-> {label}";
                         }
diff --git a/NESDecompiler.Core/ROM/ROMInfo.cs b/NESDecompiler.Core/ROM/ROMInfo.cs
index 8070747..dc243bf 100644
--- a/NESDecompiler.Core/ROM/ROMInfo.cs
+++ b/NESDecompiler.Core/ROM/ROMInfo.cs
@@ -76,7 +76,7 @@ namespace NESDecompiler.Core.ROM
         /// <summary>
         /// The raw ROM data for reference
         /// </summary>
-        public byte[] RawData { get; set; }
+        public byte[]? RawData { get; set; }
 
         /// <summary>
         /// List of identified entry points (including reset vector and NMI)
diff --git a/NESDecompiler.Core/ROM/ROMLoader.cs b/NESDecompiler.Core/ROM/ROMLoader.cs
index c62e477..2057c69 100644
--- a/NESDecompiler.Core/ROM/ROMLoader.cs
+++ b/NESDecompiler.Core/ROM/ROMLoader.cs
@@ -21,13 +21,13 @@ namespace NESDecompiler.Core.ROM
         private const int FLAGS_10_OFFSET = 10;
 
         // ROM data
-        private byte[] romData;
-        private ROMInfo romInfo;
+        private byte[]? romData;
+        private ROMInfo? romInfo;
 
         /// <summary>
         /// Information about the loaded ROM
         /// </summary>
-        public ROMInfo ROMInfo => romInfo;
+        public ROMInfo? ROMInfo => romInfo;
 
         /// <summary>
         /// Loads a NES ROM file from disk
@@ -75,7 +75,7 @@ namespace NESDecompiler.Core.ROM
         private ROMInfo ParseROMHeader()
         {
             // Verify iNES header signature "NES" followed by MS-DOS EOF
-            if (romData.Length < HEADER_SIZE ||
+            if (romData!.Length < HEADER_SIZE ||
                 romData[0] != 0x4E || romData[1] != 0x45 || romData[2] != 0x53 || romData[3] != 0x1A)
             {
                 throw new InvalidROMFormatException("Invalid iNES ROM header");