diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 246aad3bd5..d49991f792 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -16,6 +16,7 @@ steps:
   inputs:
     version: '2.1.401'
 - script: |
+    brew install castxml
     export COREHOST_TRACE=0
     export DOTNET_SKIP_FIRST_TIME_EXPERIENCE=1
     export DOTNET_CLI_TELEMETRY_OPTOUT=1