diff --git a/api/server/src/main/java/org/softwareheritage/graph/backend/Setup.java b/api/server/src/main/java/org/softwareheritage/graph/backend/Setup.java
index 42ab809..e27fe04 100644
--- a/api/server/src/main/java/org/softwareheritage/graph/backend/Setup.java
+++ b/api/server/src/main/java/org/softwareheritage/graph/backend/Setup.java
@@ -1,82 +1,83 @@
 package org.softwareheritage.graph.backend;
 
 import java.io.BufferedWriter;
 import java.io.FileInputStream;
 import java.io.FileWriter;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.Writer;
 import java.util.zip.GZIPInputStream;
 
+import it.unimi.dsi.fastutil.Size64;
 import it.unimi.dsi.fastutil.io.BinIO;
 import it.unimi.dsi.fastutil.longs.LongBigArrays;
 import it.unimi.dsi.fastutil.objects.Object2LongFunction;
 import it.unimi.dsi.fastutil.objects.ObjectBigArrays;
 import it.unimi.dsi.io.FastBufferedReader;
 import it.unimi.dsi.io.LineIterator;
 
 import org.softwareheritage.graph.backend.NodeIdMap;
 
 public class Setup {
   public static void main(String[] args) throws IOException {
     String graphPath = args[0];
 
     System.out.println("Pre-computing node id maps...");
     long startTime = System.nanoTime();
     precomputeNodeIdMap(graphPath);
     long endTime = System.nanoTime();
     double duration = (double) (endTime - startTime) / 1_000_000_000;
     System.out.println("Done in: " + duration + " seconds");
   }
 
   // Suppress warning for Object2LongFunction cast
   @SuppressWarnings("unchecked")
   static void precomputeNodeIdMap(String graphPath) throws IOException {
     // First internal mapping: SWH id (string) -> WebGraph MPH (long)
     Object2LongFunction<String> mphMap = null;
     try {
       mphMap = (Object2LongFunction<String>) BinIO.loadObject(graphPath + ".mph");
     } catch (ClassNotFoundException e) {
       throw new IllegalArgumentException("The .mph file contains unknown class object: " + e);
     }
-    long nbIds = mphMap.size();
+    long nbIds = (mphMap instanceof Size64) ? ((Size64) mphMap).size64() : mphMap.size();
 
     // Second internal mapping: WebGraph MPH (long) -> BFS ordering (long)
     long[][] bfsMap = LongBigArrays.newBigArray(nbIds);
     long loaded = BinIO.loadLongs(graphPath + ".order", bfsMap);
     if (loaded != nbIds) {
       throw new IllegalArgumentException("Graph contains " + nbIds + " nodes, but read " + loaded);
     }
 
     // Dump complete mapping for all nodes: SWH id (string) <=> WebGraph node id (long)
 
     InputStream nodeFile = new GZIPInputStream(new FileInputStream(graphPath + ".nodes.csv.gz"));
     FastBufferedReader buffer = new FastBufferedReader(new InputStreamReader(nodeFile, "UTF-8"));
     LineIterator swhIdIterator = new LineIterator(buffer);
 
     try (
         Writer swhToNodeMap = new BufferedWriter(new FileWriter(graphPath + ".swhToNodeMap.csv"));
         Writer nodeToSwhMap = new BufferedWriter(new FileWriter(graphPath + ".nodeToSwhMap.csv"))) {
       // nodeToSwhMap needs to write SWH id in order of node id, so use a temporary array
       Object[][] nodeToSwhId = ObjectBigArrays.newBigArray(nbIds);
 
       for (long iNode = 0; iNode < nbIds && swhIdIterator.hasNext(); iNode++) {
         String swhId = swhIdIterator.next().toString();
         long mphId = mphMap.getLong(swhId);
         long nodeId = LongBigArrays.get(bfsMap, mphId);
 
         String paddedNodeId = String.format("%0" + NodeIdMap.NODE_ID_LENGTH + "d", nodeId);
         String line = swhId + " " + paddedNodeId + "\n";
         swhToNodeMap.write(line);
 
         ObjectBigArrays.set(nodeToSwhId, nodeId, swhId);
       }
 
       for (long iNode = 0; iNode < nbIds; iNode++) {
         String line = ObjectBigArrays.get(nodeToSwhId, iNode).toString() + "\n";
         nodeToSwhMap.write(line);
       }
     }
   }
 }