diff --git a/azure-pipelines-ci.yml b/azure-pipelines-ci.yml
--- a/azure-pipelines-ci.yml
+++ b/azure-pipelines-ci.yml
@@ -55,6 +55,9 @@ jobs:
   pool:
     vmImage: 'macOS-10.13'
 
+  variables:
+    MACOSX_DEPLOYMENT_TARGET: 10.9
+
   steps:
   - template: azure-pipelines/templates/ci-git-rebase.yml
   - template: azure-pipelines/templates/osx-dependencies.yml
diff --git a/azure-pipelines/templates/release.yml b/azure-pipelines/templates/release.yml
--- a/azure-pipelines/templates/release.yml
+++ b/azure-pipelines/templates/release.yml
@@ -135,6 +135,9 @@ jobs:
     vmImage: 'macOS-10.13'
   dependsOn: source
 
+  variables:
+    MACOSX_DEPLOYMENT_TARGET: 10.9
+
   steps:
   - template: release-fetch-source.yml
   - template: osx-dependencies.yml