diff --git a/framework/src/Volo.Abp.AspNetCore.Authentication.OAuth/Volo.Abp.AspNetCore.Authentication.OAuth.csproj b/framework/src/Volo.Abp.AspNetCore.Authentication.OAuth/Volo.Abp.AspNetCore.Authentication.OAuth.csproj
index 562e559273..f8efe3c11c 100644
--- a/framework/src/Volo.Abp.AspNetCore.Authentication.OAuth/Volo.Abp.AspNetCore.Authentication.OAuth.csproj
+++ b/framework/src/Volo.Abp.AspNetCore.Authentication.OAuth/Volo.Abp.AspNetCore.Authentication.OAuth.csproj
@@ -5,6 +5,8 @@
 
   <PropertyGroup>
     <TargetFramework>net7.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AssemblyName>Volo.Abp.AspNetCore.Authentication.OAuth</AssemblyName>
     <PackageId>Volo.Abp.AspNetCore.Authentication.OAuth</PackageId>
     <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.AspNetCore.Authentication.OAuth/Volo/Abp/AspNetCore/Authentication/OAuth/Claims/MultipleClaimAction.cs b/framework/src/Volo.Abp.AspNetCore.Authentication.OAuth/Volo/Abp/AspNetCore/Authentication/OAuth/Claims/MultipleClaimAction.cs
index 1910af63d5..e058303572 100644
--- a/framework/src/Volo.Abp.AspNetCore.Authentication.OAuth/Volo/Abp/AspNetCore/Authentication/OAuth/Claims/MultipleClaimAction.cs
+++ b/framework/src/Volo.Abp.AspNetCore.Authentication.OAuth/Volo/Abp/AspNetCore/Authentication/OAuth/Claims/MultipleClaimAction.cs
@@ -29,7 +29,7 @@ public class MultipleClaimAction : ClaimAction
         switch (prop.ValueKind)
         {
             case JsonValueKind.String:
-                claim = new Claim(ClaimType, prop.GetString(), ValueType, issuer);
+                claim = new Claim(ClaimType, prop.GetString()!, ValueType, issuer);
                 if (!identity.Claims.Any(c => c.Type == claim.Type && c.Value == claim.Value))
                 {
                     identity.AddClaim(claim);
@@ -38,7 +38,7 @@ public class MultipleClaimAction : ClaimAction
             case JsonValueKind.Array:
                 foreach (var arramItem in prop.EnumerateArray())
                 {
-                    claim = new Claim(ClaimType, arramItem.GetString(), ValueType, issuer);
+                    claim = new Claim(ClaimType, arramItem.GetString()!, ValueType, issuer);
                     if (!identity.Claims.Any(c => c.Type == claim.Type && c.Value == claim.Value))
                     {
                         identity.AddClaim(claim);