diff --git a/src/libraries/shims/ApiCompat.proj b/src/libraries/shims/ApiCompat.proj
index d275e0efeacd82..013b95b5825e00 100644
--- a/src/libraries/shims/ApiCompat.proj
+++ b/src/libraries/shims/ApiCompat.proj
@@ -37,7 +37,7 @@
     <PropertyGroup>
       <ApiCompatImplementationDirs>$(BuildTargetFrameworkRefPath.TrimEnd('\/'))</ApiCompatImplementationDirs>
       <ApiCompatArgs Condition="'$(ApiCompatExcludeAttributeList)' != ''">$(ApiCompatArgs) --exclude-attributes "$(ApiCompatExcludeAttributeList)"</ApiCompatArgs>
-      <ApiCompatArgs>$(ApiCompatArgs) --impl-dirs "$(ApiCompatImplementationDirs)"</ApiCompatArgs>
+      <ApiCompatArgs>$(ApiCompatArgs) --impl-dirs "$(ApiCompatImplementationDirs)" --validate-baseline</ApiCompatArgs>
       <BaselineApiCompatArgs Condition="Exists($(ApiCompatBaselineIgnoreFile))">--baseline "$(ApiCompatBaselineIgnoreFile)"</BaselineApiCompatArgs>
       <ApiCompatExitCode>0</ApiCompatExitCode>
     </PropertyGroup>