diff --git a/flow-server/src/main/java/com/vaadin/flow/router/RouteNotFoundError.java b/flow-server/src/main/java/com/vaadin/flow/router/RouteNotFoundError.java
index bc3be06e248..2031b815d2e 100644
--- a/flow-server/src/main/java/com/vaadin/flow/router/RouteNotFoundError.java
+++ b/flow-server/src/main/java/com/vaadin/flow/router/RouteNotFoundError.java
@@ -18,6 +18,7 @@
 import javax.servlet.http.HttpServletResponse;
 
 import java.io.IOException;
+import java.io.InputStream;
 import java.nio.charset.StandardCharsets;
 import java.util.List;
 import java.util.stream.Collectors;
@@ -84,10 +85,9 @@ private static String getErrorHtml(boolean productionMode) {
     }
 
     private static String readHtmlFile(String templateName) {
-        try {
-            return IOUtils.toString(
-                    RouteNotFoundError.class.getResourceAsStream(templateName),
-                    StandardCharsets.UTF_8);
+        try (InputStream stream = RouteNotFoundError.class
+                .getResourceAsStream(templateName)) {
+            return IOUtils.toString(stream, StandardCharsets.UTF_8);
         } catch (IOException e) {
             LoggerFactory.getLogger(RouteNotFoundError.class)
                     .error("Unable to read " + templateName, e);