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 b4a882893..5620df42e 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
@@ -88,10 +88,6 @@ import org.eclipse.jgit.util.LongList;
  * objects are similar.
  */
 public final class DfsPackFile extends BlockBasedFile {
-	final DfsStreamKey idxKey;
-	final DfsStreamKey reverseIdxKey;
-	DfsStreamKey bitmapKey;
-
 	/**
 	 * Lock for initialization of {@link #index} and {@link #corruptObjects}.
 	 * <p>
@@ -127,8 +123,6 @@ public final class DfsPackFile extends BlockBasedFile {
 	 */
 	DfsPackFile(DfsBlockCache cache, DfsPackDescription desc) {
 		super(cache, desc, PACK);
-		idxKey = desc.getStreamKey(INDEX);
-		reverseIdxKey = idxKey.derive("r"); //$NON-NLS-1$
 		length = desc.getFileSize(PACK);
 		if (length <= 0)
 			length = -1;
@@ -151,7 +145,7 @@ public final class DfsPackFile extends BlockBasedFile {
 		long objCnt = idx.getObjectCount();
 		int recSize = Constants.OBJECT_ID_LENGTH + 8;
 		int sz = (int) Math.min(objCnt * recSize, Integer.MAX_VALUE);
-		index = cache.put(idxKey, 0, sz, idx);
+		index = cache.put(desc.getStreamKey(INDEX), 0, sz, idx);
 	}
 
 	/**
@@ -254,9 +248,7 @@ public final class DfsPackFile extends BlockBasedFile {
 				if (idx != null)
 					return idx;
 			}
-			if (bitmapKey == null) {
-				bitmapKey = desc.getStreamKey(BITMAP_INDEX);
-			}
+
 			long size;
 			PackBitmapIndex idx;
 			try {
@@ -294,8 +286,9 @@ public final class DfsPackFile extends BlockBasedFile {
 				throw e2;
 			}
 
-			bitmapIndex = cache.put(bitmapKey, 0,
-					(int) Math.min(size, Integer.MAX_VALUE), idx);
+			bitmapIndex = cache.put(
+					desc.getStreamKey(BITMAP_INDEX),
+					0, (int) Math.min(size, Integer.MAX_VALUE), idx);
 			return idx;
 		}
 	}
@@ -320,7 +313,9 @@ public final class DfsPackFile extends BlockBasedFile {
 			PackReverseIndex revidx = new PackReverseIndex(idx);
 			int sz = (int) Math.min(
 					idx.getObjectCount() * 8, Integer.MAX_VALUE);
-			reverseIndex = cache.put(reverseIdxKey, 0, sz, revidx);
+			reverseIndex = cache.put(
+					new DfsStreamKey.ForReverseIndex(desc.getStreamKey(INDEX)),
+					0, sz, revidx);
 			return revidx;
 		}
 	}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsStreamKey.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsStreamKey.java
index 5106666d5..f0a5da01f 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsStreamKey.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsStreamKey.java
@@ -80,15 +80,6 @@ public abstract class DfsStreamKey {
 		this.hash = hash * 31;
 	}
 
-	/**
-	 * Derive a new StreamKey based on this existing key.
-	 *
-	 * @param suffix
-	 *            a derivation suffix.
-	 * @return derived stream key.
-	 */
-	public abstract DfsStreamKey derive(String suffix);
-
 	@Override
 	public int hashCode() {
 		return hash;
@@ -111,14 +102,6 @@ public abstract class DfsStreamKey {
 			this.name = name;
 		}
 
-		@Override
-		public DfsStreamKey derive(String suffix) {
-			byte[] s = suffix.getBytes(UTF_8);
-			byte[] n = Arrays.copyOf(name, name.length + s.length);
-			System.arraycopy(s, 0, n, name.length, s.length);
-			return new ByteArrayDfsStreamKey(n);
-		}
-
 		@Override
 		public boolean equals(Object o) {
 			if (o instanceof ByteArrayDfsStreamKey) {
@@ -128,4 +111,19 @@ public abstract class DfsStreamKey {
 			return false;
 		}
 	}
+
+	static final class ForReverseIndex extends DfsStreamKey {
+		private final DfsStreamKey idxKey;
+
+		ForReverseIndex(DfsStreamKey idxKey) {
+			super(idxKey.hash + 1);
+			this.idxKey = idxKey;
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			return o instanceof ForReverseIndex
+					&& idxKey.equals(((ForReverseIndex) o).idxKey);
+		}
+	}
 }