diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/InlineVectorValues.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/InlineVectorValues.java
index 7e7a2751..6b63fbf2 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/InlineVectorValues.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/InlineVectorValues.java
@@ -46,7 +46,7 @@ public InlineVectorValues(int dimension, OnDiskGraphIndexWriter writer) {
 
     @Override
     public int size() {
-        return writer.getMaxOrdinal();
+        return writer.getMaxOrdinal() + 1; // +1 because ordinals are 0-based
     }
 
     @Override
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/LvqVectorValues.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/LvqVectorValues.java
index 2e830d58..cebe1374 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/LvqVectorValues.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/LvqVectorValues.java
@@ -48,7 +48,7 @@ public LvqVectorValues(int dimension, LVQ lvq, OnDiskGraphIndexWriter writer) {
 
     @Override
     public int size() {
-        return writer.getMaxOrdinal();
+        return writer.getMaxOrdinal()  + 1; // +1 because ordinals are 0-based;
     }
 
     @Override
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/OnDiskGraphIndexWriter.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/OnDiskGraphIndexWriter.java
index bac1c2fb..dfc92e28 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/OnDiskGraphIndexWriter.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/OnDiskGraphIndexWriter.java
@@ -29,7 +29,6 @@
 import java.io.RandomAccessFile;
 import java.nio.ByteBuffer;
 import java.nio.file.Path;
-import java.util.Collection;
 import java.util.EnumMap;
 import java.util.Map;
 import java.util.Set;
@@ -54,7 +53,7 @@ public class OnDiskGraphIndexWriter implements Closeable {
     private final BufferedRandomAccessWriter out;
     private final long startOffset;
     private final int headerSize;
-    private volatile int maxOrdinalWritten;
+    private volatile int maxOrdinalWritten = -1;
 
     private OnDiskGraphIndexWriter(Path outPath,
                                    int version,
@@ -115,6 +114,9 @@ public synchronized void writeInline(int ordinal, Map<FeatureId, Feature.State>
         maxOrdinalWritten = Math.max(maxOrdinalWritten, ordinal);
     }
 
+    /**
+     * @return the maximum ordinal written so far, or -1 if no ordinals have been written yet
+     */
     public int getMaxOrdinal() {
         return maxOrdinalWritten;
     }
diff --git a/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestOnDiskGraphIndex.java b/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestOnDiskGraphIndex.java
index 12d2183f..33f11444 100644
--- a/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestOnDiskGraphIndex.java
+++ b/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestOnDiskGraphIndex.java
@@ -24,6 +24,7 @@
 import io.github.jbellis.jvector.graph.ListRandomAccessVectorValues;
 import io.github.jbellis.jvector.graph.RandomAccessVectorValues;
 import io.github.jbellis.jvector.graph.TestVectorGraph;
+import io.github.jbellis.jvector.pq.LocallyAdaptiveVectorQuantization;
 import io.github.jbellis.jvector.pq.PQVectors;
 import io.github.jbellis.jvector.pq.ProductQuantization;
 import io.github.jbellis.jvector.vector.VectorSimilarityFunction;
@@ -35,18 +36,14 @@
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
-import java.util.EnumMap;
 import java.util.EnumSet;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import java.util.function.IntFunction;
 
 import static io.github.jbellis.jvector.TestUtil.getNeighborNodes;
-import static org.junit.Assert.assertArrayEquals;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.*;
 
 @ThreadLeakScope(ThreadLeakScope.Scope.NONE)
 public class TestOnDiskGraphIndex extends RandomizedTest {
@@ -275,13 +272,19 @@ public void testIncrementalWrites() throws IOException {
         var incrementalPath = testDirectory.resolve("bulk_graph");
         try (var writer = new OnDiskGraphIndexWriter.Builder(graph, incrementalPath)
                 .with(new InlineVectors(ravv.dimension()))
-                .build())
+                .build();
+             var ivv = new InlineVectorValues(ravv.dimension(), writer))
         {
+            assertEquals(0, ivv.size());
+
             // write inline vectors incrementally
             for (int i = 0; i < vectors.size(); i++) {
                 var state = Feature.singleState(FeatureId.INLINE_VECTORS, new InlineVectors.State(ravv.getVector(i)));
                 writer.writeInline(i, state);
             }
+
+            assertEquals(vectors.size(), ivv.size());
+
             // write graph structure
             writer.write(Map.of());
         }
@@ -323,5 +326,43 @@ public void testIncrementalWrites() throws IOException {
         } catch (Exception e) {
             throw new RuntimeException(e);
         }
+
+        // write incrementally with LVQ and add Fused ADC feature
+        var incrementalLvqPath = testDirectory.resolve("incremental_lvq_graph");
+        var lvq = LocallyAdaptiveVectorQuantization.compute(ravv);
+        var lvqFeature = new LVQ(lvq);
+
+        try (var writer = new OnDiskGraphIndexWriter.Builder(graph, incrementalLvqPath)
+                .with(lvqFeature)
+                .with(new FusedADC(graph.maxDegree(), pq))
+                .build();
+             var lvqvv = new LvqVectorValues(ravv.dimension(), lvqFeature, writer);)
+        {
+            assertEquals(0, lvqvv.size());
+
+            // write inline vectors incrementally
+            for (int i = 0; i < vectors.size(); i++) {
+                var state = Feature.singleState(FeatureId.LVQ, new LVQ.State(lvq.encode(ravv.getVector(i))));
+                writer.writeInline(i, state);
+            }
+
+            assertEquals(vectors.size(), lvqvv.size());
+
+            // write graph structure, fused ADC
+            writer.write(Feature.singleStateFactory(FeatureId.FUSED_ADC, i -> new FusedADC.State(graph.getView(), pqv, i)));
+            writer.write(Map.of());
+        }
+
+        // graph and vectors should be identical
+        try (var bulkMarr = new SimpleMappedReader(bulkPath.toAbsolutePath().toString());
+             var bulkGraph = OnDiskGraphIndex.load(bulkMarr::duplicate);
+             var incrementalMarr = new SimpleMappedReader(incrementalLvqPath.toAbsolutePath().toString());
+             var incrementalGraph = OnDiskGraphIndex.load(incrementalMarr::duplicate))
+        {
+            assertTrue(OnDiskGraphIndex.areHeadersEqual(incrementalGraph, bulkGraph));
+            TestUtil.assertGraphEquals(incrementalGraph, bulkGraph); // incremental and bulk graph should have same structure
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
     }
 }