diff --git a/test/extensions/geoip_providers/maxmind/geoip_provider_test.cc b/test/extensions/geoip_providers/maxmind/geoip_provider_test.cc
index b8d1cc93b647..6d3e8961d82a 100644
--- a/test/extensions/geoip_providers/maxmind/geoip_provider_test.cc
+++ b/test/extensions/geoip_providers/maxmind/geoip_provider_test.cc
@@ -94,6 +94,7 @@ class GeoipProviderTestBase {
         Registry::FactoryRegistry<Geolocation::GeoipProviderFactory>::getFactory(
             "envoy.geoip_providers.maxmind"));
     ASSERT(provider_factory_);
+    on_changed_cbs_.reserve(1);
   }
 
   ~GeoipProviderTestBase() {