diff --git a/api/server/pom.xml b/api/server/pom.xml
index a04b0e3..5429449 100644
--- a/api/server/pom.xml
+++ b/api/server/pom.xml
@@ -1,132 +1,132 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
 
     <groupId>org.softwareheritage.graph</groupId>
     <artifactId>graph</artifactId>
     <version>1.0-ALPHA</version>
 
     <name>graph</name>
     <url>https://www.softwareheritage.org/</url>
 
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <maven.compiler.release>11</maven.compiler.release>
     </properties>
 
     <dependencies>
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <version>4.11</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>org.hamcrest</groupId>
             <artifactId>hamcrest</artifactId>
             <version>2.1</version>
             <scope>test</scope>
         </dependency>
         <dependency>
             <groupId>io.javalin</groupId>
             <artifactId>javalin</artifactId>
-            <version>2.8.0</version>
+            <version>3.0.0</version>
         </dependency>
         <dependency>
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-simple</artifactId>
             <version>1.7.26</version>
         </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
             <version>2.9.8</version>
         </dependency>
         <dependency>
             <groupId>it.unimi.dsi</groupId>
             <artifactId>webgraph-big</artifactId>
             <version>3.5.0</version>
         </dependency>
         <dependency>
             <groupId>it.unimi.dsi</groupId>
             <artifactId>fastutil</artifactId>
             <version>8.2.2</version>
         </dependency>
     </dependencies>
 
     <build>
         <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
             <plugins>
                 <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
                 <plugin>
                     <artifactId>maven-clean-plugin</artifactId>
                     <version>3.1.0</version>
                 </plugin>
                 <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
                 <plugin>
                     <artifactId>maven-resources-plugin</artifactId>
                     <version>3.0.2</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-compiler-plugin</artifactId>
                     <version>3.8.0</version>
                     <configuration>
                         <compilerArgs>
                             <arg>-verbose</arg>
                             <arg>-Xlint:all</arg>
                         </compilerArgs>
                     </configuration>
                 </plugin>
                 <plugin>
                     <artifactId>maven-surefire-plugin</artifactId>
                     <version>2.22.1</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-jar-plugin</artifactId>
                     <version>3.0.2</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-install-plugin</artifactId>
                     <version>2.5.2</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-deploy-plugin</artifactId>
                     <version>2.8.2</version>
                 </plugin>
                 <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
                 <plugin>
                     <artifactId>maven-site-plugin</artifactId>
                     <version>3.7.1</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-project-info-reports-plugin</artifactId>
                     <version>3.0.0</version>
                 </plugin>
                 <plugin>
                     <artifactId>maven-assembly-plugin</artifactId>
                     <configuration>
                         <archive>
                             <manifest>
                                 <mainClass>org.softwareheritage.graph.App</mainClass>
                             </manifest>
                         </archive>
                         <descriptorRefs>
                             <descriptorRef>jar-with-dependencies</descriptorRef>
                         </descriptorRefs>
                     </configuration>
                     <executions>
                         <execution>
                             <id>make-assembly</id> <!-- this is used for inheritance merges -->
                             <phase>package</phase> <!-- bind to the packaging phase -->
                             <goals>
                                 <goal>single</goal>
                             </goals>
                         </execution>
                     </executions>
                 </plugin>
             </plugins>
         </pluginManagement>
     </build>
 </project>
diff --git a/api/server/src/main/java/org/softwareheritage/graph/App.java b/api/server/src/main/java/org/softwareheritage/graph/App.java
index 31ad1c4..d6ed0d0 100644
--- a/api/server/src/main/java/org/softwareheritage/graph/App.java
+++ b/api/server/src/main/java/org/softwareheritage/graph/App.java
@@ -1,70 +1,70 @@
 package org.softwareheritage.graph;
 
 import java.io.IOException;
 import java.util.List;
 import java.util.Map;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.PropertyNamingStrategy;
 import io.javalin.Javalin;
-import io.javalin.json.JavalinJackson;
+import io.javalin.plugin.json.JavalinJackson;
 
 import org.softwareheritage.graph.Graph;
 import org.softwareheritage.graph.SwhId;
 import org.softwareheritage.graph.algo.Stats;
 import org.softwareheritage.graph.algo.Visit;
 
 public class App {
   public static void main(String[] args) throws IOException {
     String path = args[0];
     Graph graph = new Graph(path);
     Stats stats = new Stats(path);
 
     // Clean up on exit
     Runtime.getRuntime().addShutdownHook(new Thread() {
       public void run() {
         try {
           graph.cleanUp();
         } catch (IOException e) {
           System.out.println("Could not clean up graph on exit: " + e);
         }
       }
     });
 
     // Configure Jackson JSON to use snake case naming style
     ObjectMapper objectMapper = JavalinJackson.getObjectMapper();
     objectMapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
     JavalinJackson.configure(objectMapper);
 
     Javalin app = Javalin.create().start(5010);
 
     app.get("/stats", ctx -> {
       ctx.json(stats);
     });
 
     app.get("/visit/:swh_id", ctx -> {
       try {
         Map<String, List<String>> queryParamMap = ctx.queryParamMap();
         for (String key : queryParamMap.keySet()) {
           if (!key.matches("direction|edges|traversal")) {
             throw new IllegalArgumentException("Unknown query string: " + key);
           }
         }
 
         SwhId swhId = new SwhId(ctx.pathParam("swh_id"));
 
         // By default, traversal is a forward DFS using all edges
         String traversal = ctx.queryParam("traversal", "dfs");
         String direction = ctx.queryParam("direction", "forward");
         String edges = ctx.queryParam("edges", "all");
 
         ctx.json(new Visit(graph, swhId, edges, traversal, direction));
       } catch (IllegalArgumentException e) {
         ctx.status(400);
         ctx.result(e.getMessage());
       }
     });
 
     app.error(404, ctx -> { ctx.result("Not found"); });
   }
 }