diff --git a/framework/src/Volo.Abp.ApiVersioning.Abstractions/Volo.Abp.ApiVersioning.Abstractions.csproj b/framework/src/Volo.Abp.ApiVersioning.Abstractions/Volo.Abp.ApiVersioning.Abstractions.csproj
index 038e852f21..2924448609 100644
--- a/framework/src/Volo.Abp.ApiVersioning.Abstractions/Volo.Abp.ApiVersioning.Abstractions.csproj
+++ b/framework/src/Volo.Abp.ApiVersioning.Abstractions/Volo.Abp.ApiVersioning.Abstractions.csproj
@@ -5,6 +5,8 @@
 
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AssemblyName>Volo.Abp.ApiVersioning.Abstractions</AssemblyName>
     <PackageId>Volo.Abp.ApiVersioning.Abstractions</PackageId>
     <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.ApiVersioning.Abstractions/Volo/Abp/ApiVersioning/IRequestedApiVersion.cs b/framework/src/Volo.Abp.ApiVersioning.Abstractions/Volo/Abp/ApiVersioning/IRequestedApiVersion.cs
index 96c2ef33cd..428f8bb6c0 100644
--- a/framework/src/Volo.Abp.ApiVersioning.Abstractions/Volo/Abp/ApiVersioning/IRequestedApiVersion.cs
+++ b/framework/src/Volo.Abp.ApiVersioning.Abstractions/Volo/Abp/ApiVersioning/IRequestedApiVersion.cs
@@ -2,5 +2,5 @@
 
 public interface IRequestedApiVersion
 {
-    string Current { get; }
+    string? Current { get; }
 }
diff --git a/framework/src/Volo.Abp.ApiVersioning.Abstractions/Volo/Abp/ApiVersioning/NullRequestedApiVersion.cs b/framework/src/Volo.Abp.ApiVersioning.Abstractions/Volo/Abp/ApiVersioning/NullRequestedApiVersion.cs
index 0589c662ef..6099283cc4 100644
--- a/framework/src/Volo.Abp.ApiVersioning.Abstractions/Volo/Abp/ApiVersioning/NullRequestedApiVersion.cs
+++ b/framework/src/Volo.Abp.ApiVersioning.Abstractions/Volo/Abp/ApiVersioning/NullRequestedApiVersion.cs
@@ -4,7 +4,7 @@ public class NullRequestedApiVersion : IRequestedApiVersion
 {
     public static NullRequestedApiVersion Instance = new NullRequestedApiVersion();
 
-    public string Current => null;
+    public string? Current => null;
 
     private NullRequestedApiVersion()
     {