diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/BitmapIndexImpl.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/BitmapIndexImpl.java
index 3873c3728..2c4af7068 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/BitmapIndexImpl.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/BitmapIndexImpl.java
@@ -93,17 +93,6 @@ public class BitmapIndexImpl implements BitmapIndex {
 		return new CompressedBitmap(compressed, this);
 	}
 
-	public CompressedBitmap toBitmap(PackBitmapIndex i,
-			EWAHCompressedBitmap b) {
-		if (i != packIndex) {
-			throw new IllegalArgumentException();
-		}
-		if (b == null) {
-			return null;
-		}
-		return new CompressedBitmap(b, this);
-	}
-
 	@Override
 	public CompressedBitmapBuilder newBitmapBuilder() {
 		return new CompressedBitmapBuilder(this);
@@ -327,11 +316,18 @@ public class BitmapIndexImpl implements BitmapIndex {
 		}
 	}
 
-	static final class CompressedBitmap implements Bitmap {
+	/**
+	 * Wrapper for a {@link EWAHCompressedBitmap} and {@link PackBitmapIndex}.
+	 * <p>
+	 * For a EWAHCompressedBitmap {@code bitmap} representing a vector of
+	 * bits, {@code new CompressedBitmap(bitmap, bitmapIndex)} represents the
+	 * objects at those positions in {@code bitmapIndex.packIndex}.
+	 */
+	public static final class CompressedBitmap implements Bitmap {
 		final EWAHCompressedBitmap bitmap;
 		final BitmapIndexImpl bitmapIndex;
 
-		CompressedBitmap(EWAHCompressedBitmap bitmap, BitmapIndexImpl bitmapIndex) {
+		public CompressedBitmap(EWAHCompressedBitmap bitmap, BitmapIndexImpl bitmapIndex) {
 			this.bitmap = bitmap;
 			this.bitmapIndex = bitmapIndex;
 		}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackWriterBitmapPreparer.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackWriterBitmapPreparer.java
index 63da51879..77311abaa 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackWriterBitmapPreparer.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackWriterBitmapPreparer.java
@@ -60,6 +60,7 @@ import org.eclipse.jgit.errors.IncorrectObjectTypeException;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.internal.storage.file.BitmapIndexImpl;
+import org.eclipse.jgit.internal.storage.file.BitmapIndexImpl.CompressedBitmap;
 import org.eclipse.jgit.internal.storage.file.PackBitmapIndex;
 import org.eclipse.jgit.internal.storage.file.PackBitmapIndexBuilder;
 import org.eclipse.jgit.internal.storage.file.PackBitmapIndexRemapper;
@@ -390,7 +391,7 @@ class PackWriterBitmapPreparer {
 			if (!reuse.contains(rc)) {
 				EWAHCompressedBitmap bitmap = bitmapRemapper.ofObjectType(
 						bitmapRemapper.getBitmap(rc), Constants.OBJ_COMMIT);
-				reuse.or(commitBitmapIndex.toBitmap(writeBitmaps, bitmap));
+				reuse.or(new CompressedBitmap(bitmap, commitBitmapIndex));
 			}
 		}