diff --git a/src/coreclr/crossgen-corelib.proj b/src/coreclr/crossgen-corelib.proj
index 6551f5db6ba267..1027019a412c49 100644
--- a/src/coreclr/crossgen-corelib.proj
+++ b/src/coreclr/crossgen-corelib.proj
@@ -6,7 +6,7 @@
     <ItemGroup>
       <_CoreClrBuildArg Condition="'$(TargetArchitecture)' != ''" Include="-$(TargetArchitecture)" />
       <_CoreClrBuildArg Include="-$(Configuration.ToLower())" />
-      <_CoreClrBuildArg Include="-os $(TargetOS)" />
+      <_CoreClrBuildArg Condition="!$([MSBuild]::IsOsPlatform(Windows))" Include="-os $(TargetOS)" />
     </ItemGroup>
 
     <PropertyGroup>
diff --git a/src/coreclr/runtime.proj b/src/coreclr/runtime.proj
index 344d76b2f28fef..02c4c5e205205d 100644
--- a/src/coreclr/runtime.proj
+++ b/src/coreclr/runtime.proj
@@ -10,7 +10,7 @@
       <_CoreClrBuildArg Include="$(Compiler)" />
       <_CoreClrBuildArg Condition="'$(ContinuousIntegrationBuild)' == 'true'" Include="-ci" />
       <_CoreClrBuildArg Condition="'$(CrossBuild)' == 'true'" Include="-cross" />
-      <_CoreClrBuildArg Include="-os $(TargetOS)" />
+      <_CoreClrBuildArg Condition="!$([MSBuild]::IsOsPlatform(Windows))" Include="-os $(TargetOS)" />
 
       <_CoreClrBuildArg Condition="$([MSBuild]::IsOsPlatform(Windows)) and ('$(TargetArchitecture)' == 'x86' or '$(TargetArchitecture)' == 'x64') and '$(Configuration)' == 'Release'" Include="-enforcepgo" />
       <_CoreClrBuildArg Condition="$([MSBuild]::IsOsPlatform(Windows)) and '$(CrossDac)' != ''" Include="-$(CrossDac)dac" />