When targetting .NET 9 and .NET Framework 4.8.1, NuGet throws: NU5046: The icon file 'favicon256.png' does not exist in the package.

[SetTrend]

When targetting .NET 9 and .NET Framework 4.8.1, NuGet throws:

NU5046: The icon file 'favicon256.png' does not exist in the package.

NuGet Product Used

Visual Studio 2022 v17.12.0 (MSBuild.exe)

Product Version

NuGet Version: 6.11.0.119, MSBuild-Version 17.12.6+db5f6012c for .NET Framework, dotnet version 9.0.100

Impact

I'm unable to use this version

Repro Steps & Context

This is my project file:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFrameworks>net481;net9.0-windows</TargetFrameworks>
    <LangVersion>13.0</LangVersion>
    <Nullable>enable</Nullable>
    <ImplicitUsings>disable</ImplicitUsings>
    <UseWPF>true</UseWPF>
    <ApplicationIcon>favicon.ico</ApplicationIcon>
    <DebugType>embedded</DebugType>
    <ProduceReferenceAssembly>False</ProduceReferenceAssembly>
    <GenerateDocumentationFile>True</GenerateDocumentationFile>
    <IsPublishable>False</IsPublishable>
    <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
    <Title>***</Title>
    <Description>***</Description>
    <Authors>***</Authors>
    <Product>$(PackageId)</Product>
    <Copyright>2024 – ***</Copyright>
    <PackageIcon>favicon256.png</PackageIcon>
    <PackageReadmeFile>ReadMe.md</PackageReadmeFile>
    <PackageOutputPath>$(SolutionDir)\NuGet Packages</PackageOutputPath>
    <PackageTags>***</PackageTags>
  </PropertyGroup>

  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|AnyCPU'">
    <DebugType>none</DebugType>
    <TreatWarningsAsErrors>True</TreatWarningsAsErrors>
  </PropertyGroup>

  <ItemGroup>
    <Content Include="favicon.ico" />
  </ItemGroup>

  <ItemGroup>
    <None Update="favicon256.png">
      <Pack>True</Pack>
      <PackagePath>\</PackagePath>
    </None>
    <None Update="ReadMe.md">
      <Pack>True</Pack>
      <PackagePath>\</PackagePath>
    </None>
  </ItemGroup>

</Project>

Targetting solely net9.0-windows, everything is working flawlessly. But adding the net481 target, NuGet fails.

[martinrrm]

I was able to reproduce this, if I use <TargetFramework> works, but when using <TargetFrameworks> doesn't