diff --git a/src/EnumUtilities/EnumUtilities.csproj b/src/EnumUtilities/EnumUtilities.csproj
index a28282c..0f1d13c 100644
--- a/src/EnumUtilities/EnumUtilities.csproj
+++ b/src/EnumUtilities/EnumUtilities.csproj
@@ -17,7 +17,7 @@
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+    <PackageReference Include="Polyfill" Version="4.0.0">
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diff --git a/src/EnumUtilities/packages.lock.json b/src/EnumUtilities/packages.lock.json
index 50c7559..ce67732 100644
--- a/src/EnumUtilities/packages.lock.json
+++ b/src/EnumUtilities/packages.lock.json
@@ -46,9 +46,9 @@
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+        "requested": "[4.0.0, )",
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       "Microsoft.Build.Tasks.Git": {
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