diff --git a/flow-lit-template/src/test/java/com/vaadin/flow/server/MockVaadinServletService.java b/flow-lit-template/src/test/java/com/vaadin/flow/server/MockVaadinServletService.java
index 9dbcf79f95f..c9784292f26 100644
--- a/flow-lit-template/src/test/java/com/vaadin/flow/server/MockVaadinServletService.java
+++ b/flow-lit-template/src/test/java/com/vaadin/flow/server/MockVaadinServletService.java
@@ -95,6 +95,8 @@ protected List<RequestHandler> createRequestHandlers()
 
     public void init(Instantiator instantiator) {
         this.instantiator = instantiator;
+
+        init();
     }
 
     @Override
@@ -118,7 +120,9 @@ public void init() {
                     .thenReturn(resourceProvider);
             Mockito.when(context.getAttribute(Lookup.class.getName()))
                     .thenReturn(lookup);
-            getServlet().init(config);
+            if (getServlet().getServletConfig() == null) {
+                getServlet().init(config);
+            }
             super.init();
         } catch (ServiceException | ServletException e) {
             throw new RuntimeException(e);
diff --git a/flow-polymer-template/src/test/java/com/vaadin/flow/server/MockVaadinServletService.java b/flow-polymer-template/src/test/java/com/vaadin/flow/server/MockVaadinServletService.java
index 9dbcf79f95f..c9784292f26 100644
--- a/flow-polymer-template/src/test/java/com/vaadin/flow/server/MockVaadinServletService.java
+++ b/flow-polymer-template/src/test/java/com/vaadin/flow/server/MockVaadinServletService.java
@@ -95,6 +95,8 @@ protected List<RequestHandler> createRequestHandlers()
 
     public void init(Instantiator instantiator) {
         this.instantiator = instantiator;
+
+        init();
     }
 
     @Override
@@ -118,7 +120,9 @@ public void init() {
                     .thenReturn(resourceProvider);
             Mockito.when(context.getAttribute(Lookup.class.getName()))
                     .thenReturn(lookup);
-            getServlet().init(config);
+            if (getServlet().getServletConfig() == null) {
+                getServlet().init(config);
+            }
             super.init();
         } catch (ServiceException | ServletException e) {
             throw new RuntimeException(e);