diff --git a/src/xunit.netcore.extensions/Attributes/ActiveIssueAttribute.cs b/src/xunit.netcore.extensions/Attributes/ActiveIssueAttribute.cs
index b8fbb77559..9753ab544a 100644
--- a/src/xunit.netcore.extensions/Attributes/ActiveIssueAttribute.cs
+++ b/src/xunit.netcore.extensions/Attributes/ActiveIssueAttribute.cs
@@ -14,7 +14,11 @@ namespace Xunit
     [AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
     public class ActiveIssueAttribute : Attribute, ITraitAttribute
     {
-        public ActiveIssueAttribute(int issueNumber, PlatformID platforms = PlatformID.Any) { }
-        public ActiveIssueAttribute(string issue, PlatformID platforms = PlatformID.Any) { }
+        public ActiveIssueAttribute(int issueNumber, TestPlatforms platforms = TestPlatforms.Any) { }
+        public ActiveIssueAttribute(string issue, TestPlatforms platforms = TestPlatforms.Any) { }
+
+        // TODO #999: Remove PlatformID when all uses have transitioned to TestPlatforms.
+        public ActiveIssueAttribute(int issueNumber, PlatformID platforms) { }
+        public ActiveIssueAttribute(string issue, PlatformID platforms) { }
     }
 }
diff --git a/src/xunit.netcore.extensions/Attributes/PlatformSpecificAttribute.cs b/src/xunit.netcore.extensions/Attributes/PlatformSpecificAttribute.cs
index 4ca224b9f4..e1ff21c6bd 100644
--- a/src/xunit.netcore.extensions/Attributes/PlatformSpecificAttribute.cs
+++ b/src/xunit.netcore.extensions/Attributes/PlatformSpecificAttribute.cs
@@ -14,6 +14,9 @@ namespace Xunit
     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, AllowMultiple = false)]
     public class PlatformSpecificAttribute : Attribute, ITraitAttribute
     {
+        public PlatformSpecificAttribute(TestPlatforms platforms) { }
+
+        // TODO #999: Remove PlatformID when all uses have transitioned to TestPlatforms.
         public PlatformSpecificAttribute(PlatformID platform) { }
     }
 }
diff --git a/src/xunit.netcore.extensions/Discoverers/ActiveIssueDiscoverer.cs b/src/xunit.netcore.extensions/Discoverers/ActiveIssueDiscoverer.cs
index bccb6cc11a..25ccba959e 100644
--- a/src/xunit.netcore.extensions/Discoverers/ActiveIssueDiscoverer.cs
+++ b/src/xunit.netcore.extensions/Discoverers/ActiveIssueDiscoverer.cs
@@ -28,12 +28,12 @@ public IEnumerable<KeyValuePair<string, string>> GetTraits(IAttributeInfo traitA
             Debug.Assert(ctorArgs.Count() >= 2);
 
             string issue = ctorArgs.First().ToString();
-            PlatformID platforms = (PlatformID)ctorArgs.Last();
-            if ((platforms.HasFlag(PlatformID.FreeBSD) && RuntimeInformation.IsOSPlatform(OSPlatform.Create("FREEBSD"))) ||
-                (platforms.HasFlag(PlatformID.Linux) && RuntimeInformation.IsOSPlatform(OSPlatform.Linux)) ||
-                (platforms.HasFlag(PlatformID.NetBSD) && RuntimeInformation.IsOSPlatform(OSPlatform.Create("NETBSD"))) ||
-                (platforms.HasFlag(PlatformID.OSX) && RuntimeInformation.IsOSPlatform(OSPlatform.OSX)) ||
-                (platforms.HasFlag(PlatformID.Windows) && RuntimeInformation.IsOSPlatform(OSPlatform.Windows)))
+            TestPlatforms platforms = (TestPlatforms)ctorArgs.Last();
+            if ((platforms.HasFlag(TestPlatforms.FreeBSD) && RuntimeInformation.IsOSPlatform(OSPlatform.Create("FREEBSD"))) ||
+                (platforms.HasFlag(TestPlatforms.Linux) && RuntimeInformation.IsOSPlatform(OSPlatform.Linux)) ||
+                (platforms.HasFlag(TestPlatforms.NetBSD) && RuntimeInformation.IsOSPlatform(OSPlatform.Create("NETBSD"))) ||
+                (platforms.HasFlag(TestPlatforms.OSX) && RuntimeInformation.IsOSPlatform(OSPlatform.OSX)) ||
+                (platforms.HasFlag(TestPlatforms.Windows) && RuntimeInformation.IsOSPlatform(OSPlatform.Windows)))
             {
                 yield return new KeyValuePair<string, string>(XunitConstants.Category, XunitConstants.Failing);
                 yield return new KeyValuePair<string, string>(XunitConstants.ActiveIssue, issue);
diff --git a/src/xunit.netcore.extensions/Discoverers/PlatformSpecificDiscoverer.cs b/src/xunit.netcore.extensions/Discoverers/PlatformSpecificDiscoverer.cs
index 030d6cd1d7..ce3b9e4b99 100644
--- a/src/xunit.netcore.extensions/Discoverers/PlatformSpecificDiscoverer.cs
+++ b/src/xunit.netcore.extensions/Discoverers/PlatformSpecificDiscoverer.cs
@@ -22,16 +22,16 @@ public class PlatformSpecificDiscoverer : ITraitDiscoverer
         /// <returns>The trait values.</returns>
         public IEnumerable<KeyValuePair<string, string>> GetTraits(IAttributeInfo traitAttribute)
         {
-            PlatformID platform = (PlatformID)traitAttribute.GetConstructorArguments().First();
-            if (!platform.HasFlag(PlatformID.Windows))
+            TestPlatforms platforms = (TestPlatforms)traitAttribute.GetConstructorArguments().First();
+            if (!platforms.HasFlag(TestPlatforms.Windows))
                 yield return new KeyValuePair<string, string>(XunitConstants.Category, XunitConstants.NonWindowsTest);
-            if (!platform.HasFlag(PlatformID.Linux))
+            if (!platforms.HasFlag(TestPlatforms.Linux))
                 yield return new KeyValuePair<string, string>(XunitConstants.Category, XunitConstants.NonLinuxTest);
-            if (!platform.HasFlag(PlatformID.OSX))
+            if (!platforms.HasFlag(TestPlatforms.OSX))
                 yield return new KeyValuePair<string, string>(XunitConstants.Category, XunitConstants.NonOSXTest);
-            if (!platform.HasFlag(PlatformID.FreeBSD))
+            if (!platforms.HasFlag(TestPlatforms.FreeBSD))
                 yield return new KeyValuePair<string, string>(XunitConstants.Category, XunitConstants.NonFreeBSDTest);
-            if (!platform.HasFlag(PlatformID.NetBSD))
+            if (!platforms.HasFlag(TestPlatforms.NetBSD))
                 yield return new KeyValuePair<string, string>(XunitConstants.Category, XunitConstants.NonNetBSDTest);
         }
     }
diff --git a/src/xunit.netcore.extensions/PlatformID.cs b/src/xunit.netcore.extensions/PlatformID.cs
index 988bd747f0..8d63e1e357 100644
--- a/src/xunit.netcore.extensions/PlatformID.cs
+++ b/src/xunit.netcore.extensions/PlatformID.cs
@@ -7,6 +7,7 @@
 
 namespace Xunit
 {
+    // TODO #999: Remove PlatformID when all uses have transitioned to TestPlatforms.
     [Flags]
     public enum PlatformID
     {
diff --git a/src/xunit.netcore.extensions/TestPlatforms.cs b/src/xunit.netcore.extensions/TestPlatforms.cs
new file mode 100644
index 0000000000..fe905803be
--- /dev/null
+++ b/src/xunit.netcore.extensions/TestPlatforms.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+
+namespace Xunit
+{
+    [Flags]
+    public enum TestPlatforms
+    {
+        Windows = 1,
+        Linux = 2,
+        OSX = 4,
+        FreeBSD = 8,
+        NetBSD = 16,
+        AnyUnix = FreeBSD | Linux | NetBSD | OSX,
+        Any = ~0
+    }
+}
diff --git a/src/xunit.netcore.extensions/xunit.netcore.extensions.csproj b/src/xunit.netcore.extensions/xunit.netcore.extensions.csproj
index e43d27ebaa..1068265b27 100644
--- a/src/xunit.netcore.extensions/xunit.netcore.extensions.csproj
+++ b/src/xunit.netcore.extensions/xunit.netcore.extensions.csproj
@@ -31,6 +31,7 @@
     <Compile Include="PlatformID.cs" />
     <Compile Include="SkippedTestCase.cs" />
     <Compile Include="TargetFrameworkMonikers.cs" />
+    <Compile Include="TestPlatforms.cs" />
     <Compile Include="XunitConstants.cs" />
   </ItemGroup>
   <ItemGroup>