diff --git a/lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99HnswVectorsReader.java b/lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99HnswVectorsReader.java
index faa885f7b2ea..a16e3dc8b06e 100644
--- a/lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99HnswVectorsReader.java
+++ b/lucene/core/src/java/org/apache/lucene/codecs/lucene99/Lucene99HnswVectorsReader.java
@@ -552,9 +552,11 @@ public void seek(int level, int targetOrd) throws IOException {
       arcCount = dataIn.readVInt();
       assert arcCount <= currentNeighborsBuffer.length : "too many neighbors: " + arcCount;
       if (arcCount > 0) {
-        currentNeighborsBuffer[0] = dataIn.readVInt();
-        for (int i = 1; i < arcCount; i++) {
-          currentNeighborsBuffer[i] = currentNeighborsBuffer[i - 1] + dataIn.readVInt();
+        // Faster prefix sum computation (see #14979)
+        int sum = 0;
+        for (int i = 0; i < arcCount; i++) {
+          sum += dataIn.readVInt();
+          currentNeighborsBuffer[i] = sum;
         }
       }
       arc = -1;