diff --git a/OptunaTests/OptunaTests.csproj b/OptunaTests/OptunaTests.csproj
index 85fe6d21..1306bf9d 100644
--- a/OptunaTests/OptunaTests.csproj
+++ b/OptunaTests/OptunaTests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net7.0</TargetFramework>
+    <TargetFrameworks>net48; net7.0</TargetFrameworks>
     <IsPackable>false</IsPackable>
     <IsTestProject>true</IsTestProject>
   </PropertyGroup>
diff --git a/OptunaTests/Storage/RDB/StorageTests.cs b/OptunaTests/Storage/RDB/StorageTests.cs
index de4c0655..4e7bf5f2 100644
--- a/OptunaTests/Storage/RDB/StorageTests.cs
+++ b/OptunaTests/Storage/RDB/StorageTests.cs
@@ -13,7 +13,7 @@ public class SqliteStorageTests : IClassFixture<CreateStorage>, IDisposable
     {
         private readonly string _createFilePath = @"TestFile/created.db";
         private readonly string _existFilePath = @"TestFile/sqlite.db";
-        private readonly List<string> _tempDBPaths = new();
+        private readonly List<string> _tempDBPaths = new List<string>();
 
         [Fact()]
         public void NoFileTest()
diff --git a/Tunny.CoreTests/Tunny.CoreTests.csproj b/Tunny.CoreTests/Tunny.CoreTests.csproj
index f40cd471..61e5d2d3 100644
--- a/Tunny.CoreTests/Tunny.CoreTests.csproj
+++ b/Tunny.CoreTests/Tunny.CoreTests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net7.0</TargetFramework>
+    <TargetFrameworks>net48; net7.0</TargetFrameworks>
     <IsPackable>false</IsPackable>
     <IsTestProject>true</IsTestProject>
   </PropertyGroup>