diff --git a/src/libraries/System.Linq.Parallel/src/System.Linq.Parallel.csproj b/src/libraries/System.Linq.Parallel/src/System.Linq.Parallel.csproj
index 1c349dd76cadb9..abe40ca2e317e8 100644
--- a/src/libraries/System.Linq.Parallel/src/System.Linq.Parallel.csproj
+++ b/src/libraries/System.Linq.Parallel/src/System.Linq.Parallel.csproj
@@ -1,13 +1,14 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>$(NetCoreAppCurrent)</TargetFramework>
+    <TargetFramework Condition="'$(MonoWasmBuildVariant)' != 'multithread'">$(NetCoreAppCurrent)</TargetFramework>
+    <TargetFrameworks Condition="'$(MonoWasmBuildVariant)' == 'multithread'">$(NetCoreAppCurrent);$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <UseCompilerGeneratedDocXmlFile>false</UseCompilerGeneratedDocXmlFile>
   </PropertyGroup>
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
-    <FeatureWasmThreads Condition="'$(TargetOS)' == 'browser' and '$(MonoWasmBuildVariant)' == 'multithread'">true</FeatureWasmThreads>
+    <FeatureWasmThreads Condition="'$(TargetPlatformIdentifier)' == 'browser' and '$(MonoWasmBuildVariant)' == 'multithread'">true</FeatureWasmThreads>
     <DefineConstants Condition="'$(FeatureWasmThreads)' == 'true'" >$(DefineConstants);FEATURE_WASM_THREADS</DefineConstants>
   </PropertyGroup>
   <!-- Compiled Source Files -->
diff --git a/src/libraries/System.Threading.Tasks.Parallel/src/System.Threading.Tasks.Parallel.csproj b/src/libraries/System.Threading.Tasks.Parallel/src/System.Threading.Tasks.Parallel.csproj
index ed9222b0224fb1..6332041eb43ffd 100644
--- a/src/libraries/System.Threading.Tasks.Parallel/src/System.Threading.Tasks.Parallel.csproj
+++ b/src/libraries/System.Threading.Tasks.Parallel/src/System.Threading.Tasks.Parallel.csproj
@@ -1,7 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-browser</TargetFrameworks>
+    <TargetFramework Condition="'$(MonoWasmBuildVariant)' != 'multithread'">$(NetCoreAppCurrent)</TargetFramework>
+    <TargetFrameworks Condition="'$(MonoWasmBuildVariant)' == 'multithread'">$(NetCoreAppCurrent);$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <UseCompilerGeneratedDocXmlFile>false</UseCompilerGeneratedDocXmlFile>
   </PropertyGroup>
diff --git a/src/libraries/System.Threading.Thread/ref/System.Threading.Thread.csproj b/src/libraries/System.Threading.Thread/ref/System.Threading.Thread.csproj
index d5723a09d9b9f1..af99f9b0724306 100644
--- a/src/libraries/System.Threading.Thread/ref/System.Threading.Thread.csproj
+++ b/src/libraries/System.Threading.Thread/ref/System.Threading.Thread.csproj
@@ -1,8 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>$(NetCoreAppCurrent)</TargetFramework>
-    <FeatureWasmThreads Condition="'$(TargetPlatformIdentifier)' == 'browser' and '$(MonoWasmBuildVariant)' == 'multithread'">true</FeatureWasmThreads>
-    <DefineConstants Condition="'$(FeatureWasmThreads)' == 'true'">$(DefineConstants);FEATURE_WASM_THREADS</DefineConstants>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/src/libraries/System.Threading/ref/System.Threading.csproj b/src/libraries/System.Threading/ref/System.Threading.csproj
index 7a2cbac20a48ef..48a7ddb57ebe5a 100644
--- a/src/libraries/System.Threading/ref/System.Threading.csproj
+++ b/src/libraries/System.Threading/ref/System.Threading.csproj
@@ -1,8 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>$(NetCoreAppCurrent)</TargetFramework>
-    <FeatureWasmThreads Condition="'$(TargetPlatformIdentifier)' == 'browser' and '$(MonoWasmBuildVariant)' == 'multithread'">true</FeatureWasmThreads>
-    <DefineConstants Condition="'$(FeatureWasmThreads)' == 'true'">$(DefineConstants);FEATURE_WASM_THREADS</DefineConstants>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="System.Threading.cs" />