diff --git a/src/RxFree.SourceTests.Legacy/RxFree.SourceTests.Legacy.csproj b/src/RxFree.SourceTests.Legacy/RxFree.SourceTests.Legacy.csproj
index a978e9f..82122d2 100644
--- a/src/RxFree.SourceTests.Legacy/RxFree.SourceTests.Legacy.csproj
+++ b/src/RxFree.SourceTests.Legacy/RxFree.SourceTests.Legacy.csproj
@@ -14,7 +14,7 @@
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   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.9.0" />
     <PackageReference Include="xunit" Version="2.9.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
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diff --git a/src/RxFree.SourceTests.Nullable/RxFree.SourceTests.Nullable.csproj b/src/RxFree.SourceTests.Nullable/RxFree.SourceTests.Nullable.csproj
index f9bdedb..0d77604 100644
--- a/src/RxFree.SourceTests.Nullable/RxFree.SourceTests.Nullable.csproj
+++ b/src/RxFree.SourceTests.Nullable/RxFree.SourceTests.Nullable.csproj
@@ -14,7 +14,7 @@
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   <ItemGroup>
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     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
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diff --git a/src/RxFree.SourceTests/RxFree.SourceTests.csproj b/src/RxFree.SourceTests/RxFree.SourceTests.csproj
index e716eac..6e1af05 100644
--- a/src/RxFree.SourceTests/RxFree.SourceTests.csproj
+++ b/src/RxFree.SourceTests/RxFree.SourceTests.csproj
@@ -15,7 +15,7 @@
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   <ItemGroup>
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     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
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diff --git a/src/RxFree.Tests/RxFree.Tests.csproj b/src/RxFree.Tests/RxFree.Tests.csproj
index 0dfc63a..5d7f4b0 100644
--- a/src/RxFree.Tests/RxFree.Tests.csproj
+++ b/src/RxFree.Tests/RxFree.Tests.csproj
@@ -5,7 +5,7 @@
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     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
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