diff --git a/tests/phpunit/multisite.xml b/tests/phpunit/multisite.xml
index d4361a5467..b2a2633cc6 100644
--- a/tests/phpunit/multisite.xml
+++ b/tests/phpunit/multisite.xml
@@ -25,4 +25,7 @@
             <group>ajax</group>
         </exclude>
     </groups>
+    <php>
+        <const name="WP_RUN_CORE_TESTS" value="1" />
+    </php>
 </phpunit>