diff --git a/.arcconfig b/.arcconfig
index b0eb85c..783f1d2 100644
--- a/.arcconfig
+++ b/.arcconfig
@@ -1,4 +1,3 @@
 {
-  "phabricator.uri": "https://secure.phabricator.com/",
-  "unit.engine": "PhutilUnitTestEngine"
+  "phabricator.uri": "https://secure.phabricator.com/"
 }
diff --git a/.arcunit b/.arcunit
new file mode 100644
index 0000000..860ee1a
--- /dev/null
+++ b/.arcunit
@@ -0,0 +1,8 @@
+{
+  "engines": {
+    "phutil": {
+      "type": "phutil",
+      "include": "(\\.php$)"
+    }
+  }
+}