4 files changed, 4 insertions, 4 deletions
diff --git a/src/Spv.Generator/ConstantKey.cs b/src/Spv.Generator/ConstantKey.cs
index d3c1b905..e7758b40 100644
--- a/src/Spv.Generator/ConstantKey.cs
+++ b/src/Spv.Generator/ConstantKey.cs
@@ -5,7 +5,7 @@ namespace Spv.Generator
 {
     internal struct ConstantKey : IEquatable<ConstantKey>
     {
-        private Instruction _constant;
+        private readonly Instruction _constant;
 
         public ConstantKey(Instruction constant)
         {
diff --git a/src/Spv.Generator/DeterministicStringKey.cs b/src/Spv.Generator/DeterministicStringKey.cs
index 491bb745..cab4dbcc 100644
--- a/src/Spv.Generator/DeterministicStringKey.cs
+++ b/src/Spv.Generator/DeterministicStringKey.cs
@@ -5,7 +5,7 @@ namespace Spv.Generator
 {
     internal class DeterministicStringKey : IEquatable<DeterministicStringKey>
     {
-        private string _value;
+        private readonly string _value;
 
         public DeterministicStringKey(string value)
         {
diff --git a/src/Spv.Generator/LiteralString.cs b/src/Spv.Generator/LiteralString.cs
index 629ff7bf..741d922b 100644
--- a/src/Spv.Generator/LiteralString.cs
+++ b/src/Spv.Generator/LiteralString.cs
@@ -8,7 +8,7 @@ namespace Spv.Generator
     {
         public OperandType Type => OperandType.String;
 
-        private string _value;
+        private readonly string _value;
 
         public LiteralString(string value)
         {
diff --git a/src/Spv.Generator/TypeDeclarationKey.cs b/src/Spv.Generator/TypeDeclarationKey.cs
index a4aa9563..e4fd5fd5 100644
--- a/src/Spv.Generator/TypeDeclarationKey.cs
+++ b/src/Spv.Generator/TypeDeclarationKey.cs
@@ -5,7 +5,7 @@ namespace Spv.Generator
 {
     internal struct TypeDeclarationKey : IEquatable<TypeDeclarationKey>
     {
-        private Instruction _typeDeclaration;
+        private readonly Instruction _typeDeclaration;
 
         public TypeDeclarationKey(Instruction typeDeclaration)
         {