diff --git a/java/src/main/java/org/softwareheritage/graph/experiments/topology/ConnectedComponents.java b/java/src/main/java/org/softwareheritage/graph/experiments/topology/ConnectedComponents.java
--- a/java/src/main/java/org/softwareheritage/graph/experiments/topology/ConnectedComponents.java
+++ b/java/src/main/java/org/softwareheritage/graph/experiments/topology/ConnectedComponents.java
@@ -53,7 +53,8 @@
         return config;
     }
 
-    private HashMap<Long, Long> /* ArrayList<ArrayList<Long>> */ compute(ProgressLogger pl, boolean byOrigin) throws IOException {
+    private HashMap<Long, Long> /* ArrayList<ArrayList<Long>> */ compute(ProgressLogger pl, boolean byOrigin)
+            throws IOException {
         final long n = graph.numNodes();
         final long maxN = graph.maxNodeNumber();
 
diff --git a/java/src/main/java/org/softwareheritage/graph/maps/LabelMapBuilder.java b/java/src/main/java/org/softwareheritage/graph/maps/LabelMapBuilder.java
--- a/java/src/main/java/org/softwareheritage/graph/maps/LabelMapBuilder.java
+++ b/java/src/main/java/org/softwareheritage/graph/maps/LabelMapBuilder.java
@@ -4,12 +4,9 @@
 import it.unimi.dsi.big.webgraph.LazyLongIterator;
 import it.unimi.dsi.big.webgraph.labelling.ArcLabelledImmutableGraph;
 import it.unimi.dsi.big.webgraph.labelling.BitStreamArcLabelledImmutableGraph;
-import it.unimi.dsi.fastutil.BigArrays;
 import it.unimi.dsi.fastutil.Size64;
 import it.unimi.dsi.fastutil.bytes.ByteArrays;
-import it.unimi.dsi.fastutil.io.BinIO;
 import it.unimi.dsi.fastutil.io.FastBufferedInputStream;
-import it.unimi.dsi.fastutil.longs.LongBigArrays;
 import it.unimi.dsi.fastutil.objects.Object2LongFunction;
 import it.unimi.dsi.io.OutputBitStream;
 import it.unimi.dsi.logging.ProgressLogger;
@@ -45,7 +42,8 @@
     long numFilenames;
     int totalLabelWidth;
 
-    public LabelMapBuilder(String graphPath, String debugPath, String outputGraphPath, String tmpDir) throws IOException {
+    public LabelMapBuilder(String graphPath, String debugPath, String outputGraphPath, String tmpDir)
+            throws IOException {
         this.graphPath = graphPath;
         if (outputGraphPath == null) {
             this.outputGraphPath = graphPath;
diff --git a/java/src/main/java/org/softwareheritage/graph/maps/NodeIdMap.java b/java/src/main/java/org/softwareheritage/graph/maps/NodeIdMap.java
--- a/java/src/main/java/org/softwareheritage/graph/maps/NodeIdMap.java
+++ b/java/src/main/java/org/softwareheritage/graph/maps/NodeIdMap.java
@@ -119,8 +119,8 @@
     }
 
     /**
-     * Converts byte-form SWHID to corresponding long node id.
-     * Low-level function, does not check if the SWHID is valid.
+     * Converts byte-form SWHID to corresponding long node id. Low-level function, does not check if the
+     * SWHID is valid.
      *
      * @param swhid node represented as bytes
      * @return corresponding node as a long id
diff --git a/swh/graph/tests/conftest.py b/swh/graph/tests/conftest.py
--- a/swh/graph/tests/conftest.py
+++ b/swh/graph/tests/conftest.py
@@ -10,11 +10,8 @@
 from aiohttp.test_utils import TestClient, TestServer, loop_context
 import pytest
 
-from swh.graph.backend import Backend
 from swh.graph.client import RemoteGraphClient
-from swh.graph.graph import load as graph_load
 from swh.graph.naive_client import NaiveClient
-from swh.graph.server.app import make_app
 
 SWH_GRAPH_TESTS_ROOT = Path(__file__).parents[0]
 TEST_GRAPH_PATH = SWH_GRAPH_TESTS_ROOT / "dataset/output/example"
@@ -26,6 +23,10 @@
         super().__init__(*args, **kwargs)
 
     def run(self):
+        # Lazy import to allow debian packaging
+        from swh.graph.backend import Backend
+        from swh.graph.server.app import make_app
+
         try:
             backend = Backend(graph_path=str(TEST_GRAPH_PATH))
             with loop_context() as loop:
@@ -60,5 +61,8 @@
 
 @pytest.fixture(scope="module")
 def graph():
+    # Lazy import to allow debian packaging
+    from swh.graph.graph import load as graph_load
+
     with graph_load(str(TEST_GRAPH_PATH)) as g:
         yield g