diff --git a/src/coreclr/nativeaot/System.Private.CoreLib/src/CompatibilitySuppressions.xml b/src/coreclr/nativeaot/System.Private.CoreLib/src/CompatibilitySuppressions.xml
index c410fee4e530d..d5fbde8e348dc 100644
--- a/src/coreclr/nativeaot/System.Private.CoreLib/src/CompatibilitySuppressions.xml
+++ b/src/coreclr/nativeaot/System.Private.CoreLib/src/CompatibilitySuppressions.xml
@@ -800,10 +800,6 @@
     <DiagnosticId>CP0001</DiagnosticId>
     <Target>T:System.Diagnostics.DebugAnnotations</Target>
   </Suppression>
-  <Suppression>
-    <DiagnosticId>CP0001</DiagnosticId>
-    <Target>T:System.Diagnostics.DebuggerGuidedStepThroughAttribute</Target>
-  </Suppression>
   <Suppression>
     <DiagnosticId>CP0001</DiagnosticId>
     <Target>T:System.MDArray</Target>
@@ -868,10 +864,6 @@
     <DiagnosticId>CP0001</DiagnosticId>
     <Target>T:System.Reflection.RuntimeAssemblyName</Target>
   </Suppression>
-  <Suppression>
-    <DiagnosticId>CP0001</DiagnosticId>
-    <Target>T:System.Runtime.CompilerServices.EagerStaticClassConstructionAttribute</Target>
-  </Suppression>
   <Suppression>
     <DiagnosticId>CP0001</DiagnosticId>
     <Target>T:System.Runtime.CompilerServices.ForceDictionaryLookupsAttribute</Target>
@@ -1006,8 +998,4 @@
     <Left>ref/net8.0/System.Private.CoreLib.dll</Left>
     <Right>lib/net8.0/System.Private.CoreLib.dll</Right>
   </Suppression>
-  <Suppression>
-    <DiagnosticId>CP0016</DiagnosticId>
-    <Target>M:System.Runtime.InteropServices.Marshal.GetObjectForNativeVariant``1(System.IntPtr)-&gt;T?:[T:System.Diagnostics.CodeAnalysis.MaybeNullAttribute]</Target>
-  </Suppression>
-</Suppressions>
\ No newline at end of file
+</Suppressions>
diff --git a/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.Com.cs b/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.Com.cs
index ba72bcaad12f3..18828c7ad17f7 100644
--- a/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.Com.cs
+++ b/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.Com.cs
@@ -342,10 +342,9 @@ public static object GetObjectForIUnknown(IntPtr pUnk)
             }
         }
 
-        [return: MaybeNull]
         [SupportedOSPlatform("windows")]
         [EditorBrowsable(EditorBrowsableState.Never)]
-        public static T GetObjectForNativeVariant<T>(IntPtr pSrcNativeVariant)
+        public static T? GetObjectForNativeVariant<T>(IntPtr pSrcNativeVariant)
         {
             throw new NotSupportedException(SR.PlatformNotSupported_ComInterop);
         }
diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/src/CompatibilitySuppressions.WasmThreads.xml b/src/libraries/System.Runtime.InteropServices.JavaScript/src/CompatibilitySuppressions.WasmThreads.xml
new file mode 100644
index 0000000000000..5f6463b613136
--- /dev/null
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/src/CompatibilitySuppressions.WasmThreads.xml
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Suppressions xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
+  <Suppression>
+    <DiagnosticId>CP0001</DiagnosticId>
+    <Target>T:System.Runtime.InteropServices.JavaScript.WebWorker</Target>
+    <Left>ref/net8.0/System.Runtime.InteropServices.JavaScript.dll</Left>
+    <Right>runtimes/browser/lib/net8.0/System.Runtime.InteropServices.JavaScript.dll</Right>
+  </Suppression>
+</Suppressions>
diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/src/CompatibilitySuppressions.xml b/src/libraries/System.Runtime.InteropServices.JavaScript/src/CompatibilitySuppressions.xml
index ce09898be3a45..0f9c4fcf9fb0f 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/src/CompatibilitySuppressions.xml
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/src/CompatibilitySuppressions.xml
@@ -43,12 +43,6 @@
     <Left>ref/net8.0/System.Runtime.InteropServices.JavaScript.dll</Left>
     <Right>runtimes/browser/lib/net8.0/System.Runtime.InteropServices.JavaScript.dll</Right>
   </Suppression>
-  <Suppression>
-    <DiagnosticId>CP0001</DiagnosticId>
-    <Target>T:System.Runtime.InteropServices.JavaScript.WebWorker</Target>
-    <Left>ref/net8.0/System.Runtime.InteropServices.JavaScript.dll</Left>
-    <Right>runtimes/browser/lib/net8.0/System.Runtime.InteropServices.JavaScript.dll</Right>
-  </Suppression>
   <Suppression>
     <DiagnosticId>CP0001</DiagnosticId>
     <Target>T:System.Runtime.InteropServices.JavaScript.CancelablePromise</Target>
@@ -67,4 +61,4 @@
     <Left>ref/net8.0/System.Runtime.InteropServices.JavaScript.dll</Left>
     <Right>runtimes/browser/lib/net8.0/System.Runtime.InteropServices.JavaScript.dll</Right>
   </Suppression>
-</Suppressions>
\ No newline at end of file
+</Suppressions>
diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/src/System.Runtime.InteropServices.JavaScript.csproj b/src/libraries/System.Runtime.InteropServices.JavaScript/src/System.Runtime.InteropServices.JavaScript.csproj
index 3cc3478d9f491..33a44fdb05cd7 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/src/System.Runtime.InteropServices.JavaScript.csproj
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/src/System.Runtime.InteropServices.JavaScript.csproj
@@ -78,6 +78,9 @@
     <Compile Include="System\Runtime\InteropServices\JavaScript\WebWorker.cs" />
     <Compile Include="System\Runtime\InteropServices\JavaScript\JSSynchronizationContext.cs" />
   </ItemGroup>
+  <ItemGroup Condition="'$(MonoWasmBuildVariant)' == 'multithread'">
+    <ApiCompatSuppressionFile Include="CompatibilitySuppressions.xml;CompatibilitySuppressions.WasmThreads.xml" />
+  </ItemGroup>
 
   <ItemGroup>
     <Reference Include="System.Collections" />
@@ -90,7 +93,7 @@
     <Reference Include="System.Threading.Thread" />
     <Reference Include="System.Threading.Channels" />
   </ItemGroup>
-  
+
   <ItemGroup>
     <ProjectReference Include="$(LibrariesProjectRoot)System.Runtime.InteropServices\gen\Microsoft.Interop.SourceGeneration\Microsoft.Interop.SourceGeneration.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
     <ProjectReference Include="$(LibrariesProjectRoot)System.Runtime.InteropServices.JavaScript\gen\JSImportGenerator\JSImportGenerator.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />