diff --git a/src/System.Buffers/src/System.Buffers.csproj b/src/System.Buffers/src/System.Buffers.csproj
index 8fc8d5eb7619..0b10d1399292 100644
--- a/src/System.Buffers/src/System.Buffers.csproj
+++ b/src/System.Buffers/src/System.Buffers.csproj
@@ -6,7 +6,8 @@
     <ProjectGuid>{2ADDB484-6F57-4D71-A3FE-A57EC6329A2B}</ProjectGuid>
     <PackageTargetFramework>dotnet5.2</PackageTargetFramework>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <UseOpenKey>true</UseOpenKey>
+    <!-- Disable Open Key on cross plat since Roslyn doesn't support it yet. -->
+    <UseOpenKey Condition="'$(OsEnvironment)'=='Windows_NT'>true</UseOpenKey>
   </PropertyGroup>
   <!-- Default configurations to help VS understand the options -->
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|AnyCPU'" />
diff --git a/src/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj b/src/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj
index b498839d5f87..601e44421cda 100644
--- a/src/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj
+++ b/src/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj
@@ -7,7 +7,8 @@
     <AssemblyVersion>4.0.0.0</AssemblyVersion>
     <DocumentationFile>$(OutputPath)$(AssemblyName).xml</DocumentationFile>
     <PackageTargetFramework>dotnet5.2</PackageTargetFramework>
-    <UseOpenKey>true</UseOpenKey>
+    <!-- Disable Open Key on cross plat since Roslyn doesn't support it yet. -->
+    <UseOpenKey Condition="'$(OsEnvironment)'=='Windows_NT'">true</UseOpenKey>
   </PropertyGroup>
   <!-- Default configurations to help VS understand the configurations -->
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
diff --git a/src/System.Text.Encodings.Web/src/System.Text.Encodings.Web.csproj b/src/System.Text.Encodings.Web/src/System.Text.Encodings.Web.csproj
index 4deb9724da99..1516eda6b101 100644
--- a/src/System.Text.Encodings.Web/src/System.Text.Encodings.Web.csproj
+++ b/src/System.Text.Encodings.Web/src/System.Text.Encodings.Web.csproj
@@ -8,7 +8,8 @@
     <AssemblyVersion>4.0.0.0</AssemblyVersion>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <PackageTargetFramework>dotnet5.1</PackageTargetFramework>
-    <UseOpenKey>true</UseOpenKey>
+    <!-- Disable Open Key on cross plat since Roslyn doesn't support it yet. -->
+    <UseOpenKey Condition="'$(OsEnvironment)'=='Windows_NT'>true</UseOpenKey>
   </PropertyGroup>
   <!-- Default configurations to help VS understand the configurations -->
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
diff --git a/src/System.Threading.Tasks.Extensions/src/System.Threading.Tasks.Extensions.csproj b/src/System.Threading.Tasks.Extensions/src/System.Threading.Tasks.Extensions.csproj
index 70cbfbf64e20..92227c227d58 100644
--- a/src/System.Threading.Tasks.Extensions/src/System.Threading.Tasks.Extensions.csproj
+++ b/src/System.Threading.Tasks.Extensions/src/System.Threading.Tasks.Extensions.csproj
@@ -7,7 +7,8 @@
     <AssemblyVersion>4.0.0.0</AssemblyVersion>
     <DocumentationFile>$(OutputPath)$(AssemblyName).xml</DocumentationFile>
     <PackageTargetFramework>dotnet5.1</PackageTargetFramework>
-    <UseOpenKey>true</UseOpenKey>
+    <!-- Disable Open Key on cross plat since Roslyn doesn't support it yet. -->
+    <UseOpenKey Condition="'$(OsEnvironment)'=='Windows_NT'>true</UseOpenKey>
   </PropertyGroup>
   <!-- Default configurations to help VS understand the configurations -->
   <PropertyGroup Condition="'$(Configuration)|$(Platform)' == 'Debug|AnyCPU'" />