diff --git a/src/JanusGraph.Net/IO/GraphBinary/JanusGraphTypeSerializerRegistry.cs b/src/JanusGraph.Net/IO/GraphBinary/JanusGraphTypeSerializerRegistry.cs
index 0ac8ba6..48be44e 100644
--- a/src/JanusGraph.Net/IO/GraphBinary/JanusGraphTypeSerializerRegistry.cs
+++ b/src/JanusGraph.Net/IO/GraphBinary/JanusGraphTypeSerializerRegistry.cs
@@ -37,7 +37,7 @@ public static class JanusGraphTypeSerializerRegistry
         /// </summary>
         public static readonly TypeSerializerRegistry Instance = Build().Create();
 
-        private static Builder Build() => new Builder();
+        private static Builder Build() => new();
 
         /// <summary>
         ///     Builds a <see cref="TypeSerializerRegistry" /> with serializers for JanusGraph types already registered.
diff --git a/src/JanusGraph.Net/IO/GraphBinary/Types/JanusGraphTypeSerializer.cs b/src/JanusGraph.Net/IO/GraphBinary/Types/JanusGraphTypeSerializer.cs
index 9180952..4ce3590 100644
--- a/src/JanusGraph.Net/IO/GraphBinary/Types/JanusGraphTypeSerializer.cs
+++ b/src/JanusGraph.Net/IO/GraphBinary/Types/JanusGraphTypeSerializer.cs
@@ -43,7 +43,7 @@ protected JanusGraphTypeSerializer(GraphBinaryType type)
         }
 
         /// <inheritdoc />
-        public override async Task WriteAsync(object value, Stream stream, GraphBinaryWriter writer,
+        public override async Task WriteAsync(object? value, Stream stream, GraphBinaryWriter writer,
             CancellationToken cancellationToken = default)
         {
             await stream.WriteIntAsync(_type.TypeId, cancellationToken).ConfigureAwait(false);
@@ -52,7 +52,7 @@ public override async Task WriteAsync(object value, Stream stream, GraphBinaryWr
         }
 
         /// <inheritdoc />
-        public override async Task WriteNullableValueAsync(object value, Stream stream, GraphBinaryWriter writer,
+        public override async Task WriteNullableValueAsync(object? value, Stream stream, GraphBinaryWriter writer,
             CancellationToken cancellationToken = default)
         {
             if (value == null)
@@ -90,7 +90,7 @@ protected abstract Task WriteNonNullableValueInternalAsync(object value, Stream
             GraphBinaryWriter writer, CancellationToken cancellationToken = default);
 
         /// <inheritdoc />
-        public override async Task<object> ReadAsync(Stream stream, GraphBinaryReader reader,
+        public override async Task<object?> ReadAsync(Stream stream, GraphBinaryReader reader,
             CancellationToken cancellationToken = default)
         {
             var customTypeInfo = await stream.ReadIntAsync(cancellationToken).ConfigureAwait(false);
@@ -104,7 +104,7 @@ public override async Task<object> ReadAsync(Stream stream, GraphBinaryReader re
         }
 
         /// <inheritdoc />
-        public override async Task<object> ReadNullableValueAsync(Stream stream, GraphBinaryReader reader,
+        public override async Task<object?> ReadNullableValueAsync(Stream stream, GraphBinaryReader reader,
             CancellationToken cancellationToken = default)
         {
             var valueFlag = await stream.ReadByteAsync(cancellationToken).ConfigureAwait(false);
diff --git a/src/JanusGraph.Net/IO/GraphBinary/Types/RelationIdentifierSerializer.cs b/src/JanusGraph.Net/IO/GraphBinary/Types/RelationIdentifierSerializer.cs
index fcfe407..0f821fa 100644
--- a/src/JanusGraph.Net/IO/GraphBinary/Types/RelationIdentifierSerializer.cs
+++ b/src/JanusGraph.Net/IO/GraphBinary/Types/RelationIdentifierSerializer.cs
@@ -109,7 +109,7 @@ public override async Task<object> ReadNonNullableValueAsync(Stream stream,
             var relationId = await stream.ReadLongAsync(cancellationToken).ConfigureAwait(false);
 
             var inVertexIdMarker = await stream.ReadByteAsync(cancellationToken).ConfigureAwait(false);
-            object inVertexId;
+            object? inVertexId;
             if (inVertexIdMarker == StringMarker)
             {
                 inVertexId = await ReadStringAsync(stream, cancellationToken).ConfigureAwait(false);
diff --git a/src/JanusGraph.Net/IO/GraphSON/JanusGraphGraphSONMessageSerializer.cs b/src/JanusGraph.Net/IO/GraphSON/JanusGraphGraphSONMessageSerializer.cs
index dea358b..992f694 100644
--- a/src/JanusGraph.Net/IO/GraphSON/JanusGraphGraphSONMessageSerializer.cs
+++ b/src/JanusGraph.Net/IO/GraphSON/JanusGraphGraphSONMessageSerializer.cs
@@ -60,7 +60,7 @@ public async Task<byte[]> SerializeMessageAsync(RequestMessage requestMessage,
         }
 
         /// <inheritdoc />
-        public async Task<ResponseMessage<List<object>>> DeserializeMessageAsync(byte[] message,
+        public async Task<ResponseMessage<List<object>>?> DeserializeMessageAsync(byte[] message,
             CancellationToken cancellationToken = default)
         {
             return await _serializer.DeserializeMessageAsync(message, cancellationToken).ConfigureAwait(false);
diff --git a/src/JanusGraph.Net/IO/GraphSON/RelationIdentifierDeserializer.cs b/src/JanusGraph.Net/IO/GraphSON/RelationIdentifierDeserializer.cs
index 7be317b..08558cb 100644
--- a/src/JanusGraph.Net/IO/GraphSON/RelationIdentifierDeserializer.cs
+++ b/src/JanusGraph.Net/IO/GraphSON/RelationIdentifierDeserializer.cs
@@ -27,7 +27,7 @@ internal class RelationIdentifierDeserializer : IGraphSONDeserializer
     {
         public dynamic Objectify(JsonElement graphsonObject, GraphSONReader reader)
         {
-            return new RelationIdentifier(graphsonObject.GetProperty("relationId").GetString());
+            return new RelationIdentifier(graphsonObject.GetProperty("relationId").GetString()!);
         }
     }
 }
\ No newline at end of file
diff --git a/src/JanusGraph.Net/JanusGraph.Net.csproj b/src/JanusGraph.Net/JanusGraph.Net.csproj
index b364425..20adec6 100644
--- a/src/JanusGraph.Net/JanusGraph.Net.csproj
+++ b/src/JanusGraph.Net/JanusGraph.Net.csproj
@@ -6,6 +6,8 @@
     <IncludeSource>True</IncludeSource>
     <IncludeSymbols>True</IncludeSymbols>
     <SymbolPackageFormat>snupkg</SymbolPackageFormat>
+    <LangVersion>9</LangVersion>
+    <Nullable>enable</Nullable>
     <Version>1.0.0-rc2</Version>
     <Title>JanusGraph.Net</Title>
     <Authors>JanusGraph</Authors>
diff --git a/src/JanusGraph.Net/JanusGraphClientBuilder.cs b/src/JanusGraph.Net/JanusGraphClientBuilder.cs
index ebac628..f8a6b76 100644
--- a/src/JanusGraph.Net/JanusGraphClientBuilder.cs
+++ b/src/JanusGraph.Net/JanusGraphClientBuilder.cs
@@ -37,8 +37,8 @@ public class JanusGraphClientBuilder
         private readonly GremlinServer _server;
         private readonly JanusGraphSONReaderBuilder _readerBuilder = JanusGraphSONReaderBuilder.Build();
         private readonly JanusGraphSONWriterBuilder _writerBuilder;
-        private IMessageSerializer _serializer;
-        private ConnectionPoolSettings _connectionPoolSettings;
+        private IMessageSerializer? _serializer;
+        private ConnectionPoolSettings? _connectionPoolSettings;
 
         private JanusGraphClientBuilder(GremlinServer server)
         {
diff --git a/src/JanusGraph.Net/JanusGraphP.cs b/src/JanusGraph.Net/JanusGraphP.cs
index da7ab83..d7c9467 100644
--- a/src/JanusGraph.Net/JanusGraphP.cs
+++ b/src/JanusGraph.Net/JanusGraphP.cs
@@ -24,7 +24,7 @@ namespace JanusGraph.Net
 {
     internal class JanusGraphP : P
     {
-        public JanusGraphP(string operatorName, object value, P other = null) : base(operatorName, value, other)
+        public JanusGraphP(string operatorName, object? value, P? other = null) : base(operatorName, value, other)
         {
         }
     }
diff --git a/src/JanusGraph.Net/RelationIdentifier.cs b/src/JanusGraph.Net/RelationIdentifier.cs
index 0f58d36..ffcd375 100644
--- a/src/JanusGraph.Net/RelationIdentifier.cs
+++ b/src/JanusGraph.Net/RelationIdentifier.cs
@@ -73,7 +73,7 @@ public RelationIdentifier(string stringRepresentation)
         /// <param name="typeId">The JanusGraph internal type id.</param>
         /// <param name="relationId">The JanusGraph internal relation id.</param>
         /// <param name="inVertexId">The id of the incoming vertex.</param>
-        public RelationIdentifier(object outVertexId, long typeId, long relationId, object inVertexId)
+        public RelationIdentifier(object outVertexId, long typeId, long relationId, object? inVertexId)
         {
             OutVertexId = outVertexId;
             TypeId = typeId;
@@ -132,10 +132,10 @@ public RelationIdentifier(object outVertexId, long typeId, long relationId, obje
         /// <summary>
         ///     Gets the id of the incoming vertex.
         /// </summary>
-        public object InVertexId { get; }
+        public object? InVertexId { get; }
 
         /// <inheritdoc />
-        public bool Equals(RelationIdentifier other)
+        public bool Equals(RelationIdentifier? other)
         {
             if (ReferenceEquals(null, other)) return false;
             if (ReferenceEquals(this, other)) return true;
@@ -143,7 +143,7 @@ public bool Equals(RelationIdentifier other)
         }
 
         /// <inheritdoc />
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             if (ReferenceEquals(null, obj)) return false;
             if (ReferenceEquals(this, obj)) return true;
@@ -154,7 +154,7 @@ public override bool Equals(object obj)
         /// <inheritdoc />
         public override int GetHashCode()
         {
-            return StringRepresentation != null ? StringRepresentation.GetHashCode() : 0;
+            return StringRepresentation.GetHashCode();
         }
 
         /// <inheritdoc />