diff --git a/src/System.Diagnostics.Tracing/tests/BasicEventSourceTest/TestsEventSourceLifetime.cs b/src/System.Diagnostics.Tracing/tests/BasicEventSourceTest/TestsEventSourceLifetime.cs
index d2ab44c81a46..dd7d2e36183b 100644
--- a/src/System.Diagnostics.Tracing/tests/BasicEventSourceTest/TestsEventSourceLifetime.cs
+++ b/src/System.Diagnostics.Tracing/tests/BasicEventSourceTest/TestsEventSourceLifetime.cs
@@ -20,7 +20,7 @@ public class TestsEventSourceLifetime
         /// alive.
         /// </summary>
         [Fact]
-        [PlatformSpecific(PlatformID.Windows)] // non-Windows EventSources don't have lifetime
+        [PlatformSpecific(Xunit.PlatformID.Windows)] // non-Windows EventSources don't have lifetime
         public void Test_EventSource_Lifetime()
         {
             TestUtilities.CheckNoEventSourcesRunning("Start");
diff --git a/src/System.Runtime/tests/System/GCTests.cs b/src/System.Runtime/tests/System/GCTests.cs
index 6efadf34009a..6768bba52930 100644
--- a/src/System.Runtime/tests/System/GCTests.cs
+++ b/src/System.Runtime/tests/System/GCTests.cs
@@ -398,7 +398,7 @@ public static void LatencyRoundtrips(GCLatencyMode value)
         }
 
         [Theory]
-        [PlatformSpecific(PlatformID.Windows)] //Concurent GC is not enabled on Unix. Recombine to TestLatencyRoundTrips once addressed.
+        [PlatformSpecific(Xunit.PlatformID.Windows)] //Concurent GC is not enabled on Unix. Recombine to TestLatencyRoundTrips once addressed.
         [InlineData(GCLatencyMode.LowLatency)]
         [InlineData(GCLatencyMode.SustainedLowLatency)]
         public static void LatencyRoundtrips_LowLatency(GCLatencyMode value) => LatencyRoundtrips(value);
diff --git a/src/System.Runtime/tests/System/Threading/WaitHandleTests.cs b/src/System.Runtime/tests/System/Threading/WaitHandleTests.cs
index d4e9f2e3508c..796620b0cc1a 100644
--- a/src/System.Runtime/tests/System/Threading/WaitHandleTests.cs
+++ b/src/System.Runtime/tests/System/Threading/WaitHandleTests.cs
@@ -84,7 +84,7 @@ public static void WaitAll_SameHandles()
         }
 
         [Fact]
-        [PlatformSpecific(PlatformID.Windows)] // names aren't supported on Unix
+        [PlatformSpecific(Xunit.PlatformID.Windows)] // names aren't supported on Unix
         public static void WaitAll_SameNames()
         {
             Mutex[] wh = new Mutex[2];
diff --git a/src/System.Runtime/tests/System/TimeZoneInfoTests.cs b/src/System.Runtime/tests/System/TimeZoneInfoTests.cs
index 539ec38cd998..d0df110b4f63 100644
--- a/src/System.Runtime/tests/System/TimeZoneInfoTests.cs
+++ b/src/System.Runtime/tests/System/TimeZoneInfoTests.cs
@@ -1671,7 +1671,7 @@ public static void IsInvalidTime()
         }
 
         [Fact]
-        [PlatformSpecific(PlatformID.AnyUnix)]
+        [PlatformSpecific(Xunit.PlatformID.AnyUnix)]
         public static void IsDaylightSavingTime_CatamarcaMultiYearDaylightSavings()
         {
             // America/Catamarca had DST from
@@ -1694,7 +1694,7 @@ public static void IsDaylightSavingTime_CatamarcaMultiYearDaylightSavings()
         }
 
         [Theory]
-        [PlatformSpecific(PlatformID.AnyUnix)]
+        [PlatformSpecific(Xunit.PlatformID.AnyUnix)]
         [InlineData("1940-02-24T23:59:59.0000000Z", false, "0:00:00")]
         [InlineData("1940-02-25T00:00:00.0000000Z", true, "1:00:00")]
         [InlineData("1940-11-20T00:00:00.0000000Z", true, "1:00:00")]
@@ -1718,7 +1718,7 @@ public static void IsDaylightSavingTime_CasablancaMultiYearDaylightSavings(strin
         }
 
         [Theory]
-        [PlatformSpecific(PlatformID.AnyUnix)]
+        [PlatformSpecific(Xunit.PlatformID.AnyUnix)]
         // in 1996 Europe/Lisbon changed from standard time to DST without changing the UTC offset
         [InlineData("1995-09-30T17:00:00.0000000Z", false, "1:00:00")]
         [InlineData("1996-03-31T00:59:59.0000000Z", false, "1:00:00")]
@@ -1835,7 +1835,7 @@ public static void DaylightTransitionsExactTime()
         /// See https://github.com/dotnet/coreclr/issues/2185
         /// </summary>
         [Fact]
-        [PlatformSpecific(PlatformID.AnyUnix)]
+        [PlatformSpecific(Xunit.PlatformID.AnyUnix)]
         public static void DaylightTransitionsExactTime_Johannesburg()
         {
             DateTimeOffset transition = new DateTimeOffset(1943, 3, 20, 23, 0, 0, TimeSpan.Zero);