diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/PackReverseIndexTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/PackReverseIndexTest.java
index 292e3e758..cd37c354a 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/PackReverseIndexTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/PackReverseIndexTest.java
@@ -37,9 +37,8 @@ public class PackReverseIndexTest extends RepositoryTestCase {
 	public void setUp() throws Exception {
 		super.setUp();
 		// index with both small (< 2^31) and big offsets
-		idx = PackIndex.open(JGitTestUtil.getTestResourceFile(
-				"pack-huge.idx"));
-		reverseIdx = new PackReverseIndex(idx);
+		idx = PackIndex.open(JGitTestUtil.getTestResourceFile("pack-huge.idx"));
+		reverseIdx = PackReverseIndex.computeFromIndex(idx);
 	}
 
 	/**
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFile.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFile.java
index c745b8e6e..466d5d435 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFile.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsPackFile.java
@@ -1068,7 +1068,7 @@ private DfsBlockCache.Ref<PackReverseIndex> loadReverseIdx(
 			DfsReader ctx, DfsStreamKey revKey, PackIndex idx) {
 		ctx.stats.readReverseIdx++;
 		long start = System.nanoTime();
-		PackReverseIndex revidx = new PackReverseIndex(idx);
+		PackReverseIndex revidx = PackReverseIndex.computeFromIndex(idx);
 		reverseIndex = revidx;
 		ctx.stats.readReverseIdxMicros += elapsedMicros(start);
 		return new DfsBlockCache.Ref<>(
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/Pack.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/Pack.java
index 6e74136c1..5d401f451 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/Pack.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/Pack.java
@@ -1148,7 +1148,7 @@ synchronized PackBitmapIndex getBitmapIndex() throws IOException {
 
 	private synchronized PackReverseIndex getReverseIdx() throws IOException {
 		if (reverseIdx == null)
-			reverseIdx = new PackReverseIndex(idx());
+			reverseIdx = PackReverseIndex.computeFromIndex(idx());
 		return reverseIdx;
 	}
 
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackReverseIndex.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackReverseIndex.java
index 1a5adb4a1..fdbd36413 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackReverseIndex.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackReverseIndex.java
@@ -48,6 +48,19 @@ public class PackReverseIndex {
 	/** Mapping from indices in offset order to indices in SHA-1 order. */
 	private final int[] nth;
 
+	/**
+	 * Compute an in-memory pack reverse index from the in-memory pack forward
+	 * index. This computation uses insertion sort, which has a quadratic
+	 * runtime on average.
+	 *
+	 * @param packIndex
+	 *            the forward index to compute from
+	 * @return the reverse index instance
+	 */
+	public static PackReverseIndex computeFromIndex(PackIndex packIndex) {
+		return new PackReverseIndex(packIndex);
+	}
+
 	/**
 	 * Create reverse index from straight/forward pack index, by indexing all
 	 * its entries.
@@ -55,7 +68,7 @@ public class PackReverseIndex {
 	 * @param packIndex
 	 *            forward index - entries to (reverse) index.
 	 */
-	public PackReverseIndex(PackIndex packIndex) {
+	private PackReverseIndex(PackIndex packIndex) {
 		index = packIndex;
 
 		final long cnt = index.getObjectCount();