diff --git a/codex/manifest/coders.nim b/codex/manifest/coders.nim
index ee876265..155157fe 100644
--- a/codex/manifest/coders.nim
+++ b/codex/manifest/coders.nim
@@ -60,7 +60,8 @@ proc encode*(coder: DagPBCoder, manifest: Manifest): ?!seq[byte] =
     var erasureInfo = initProtoBuffer()
     erasureInfo.write(1, manifest.ecK.uint32)
     erasureInfo.write(2, manifest.ecM.uint32)
-    erasureInfo.write(3, ? coder.encode(manifest.originalManifest)) # TODO: fix check
+    erasureInfo.write(3, manifest.interleave.uint32)
+    erasureInfo.write(4, ? coder.encode(manifest.originalManifest)) # TODO: fix check
     erasureInfo.finish()
 
     header.write(4, erasureInfo)
@@ -82,7 +83,7 @@ proc decode*(coder: DagPBCoder, data: openArray[byte]): ?!Manifest =
     originalManifest: Manifest
     datasetSize: uint32
     blockSize: uint32
-    ecK, ecM: uint32
+    ecK, ecM, interleave: uint32
 
   # Decode `Header` message
   if pbNode.getField(1, pbHeader).isErr:
@@ -109,8 +110,11 @@ proc decode*(coder: DagPBCoder, data: openArray[byte]): ?!Manifest =
     if pbErasureInfo.getField(2, ecM).isErr:
       return failure("Unable to decode `M` from manifest!")
 
+    if pbErasureInfo.getField(3, interleave).isErr:
+      return failure("Unable to decode `interleave` from manifest!")
+
     var buffer = newSeq[byte]()
-    if pbErasureInfo.getField(3, buffer).isErr:
+    if pbErasureInfo.getField(4, buffer).isErr:
       return failure("Unable to decode `originalManifest` from manifest!")
     originalManifest = coder.decode(buffer).get # TODO: fix check
 
@@ -128,7 +132,8 @@ proc decode*(coder: DagPBCoder, data: openArray[byte]): ?!Manifest =
         codec = treeCid.mcodec,
         ecK = ecK.int,
         ecM = ecM.int,
-        originalManifest originalManifest
+        interleave = interleave.int, #TODO
+        originalManifest = originalManifest
       )
       else:
         Manifest.new(
diff --git a/codex/manifest/manifest.nim b/codex/manifest/manifest.nim
index db7c341e..8499ff17 100644
--- a/codex/manifest/manifest.nim
+++ b/codex/manifest/manifest.nim
@@ -40,6 +40,7 @@ type
     of true:
       ecK: int                              # Number of blocks to encode
       ecM: int                              # Number of resulting parity blocks
+      interleave: int                       # How far apart are blocks of an erasure code according to original index
       originalManifest: Manifest            # The original Manifest being erasure coded
     else:
       discard
@@ -72,6 +73,9 @@ proc ecK*(self: Manifest): int =
 proc ecM*(self: Manifest): int =
   self.ecM
 
+proc interleave*(self: Manifest): int =
+  self.interleave
+
 proc originalManifest*(self: Manifest): Manifest =
   self.originalManifest
 
@@ -119,7 +123,7 @@ func rounded*(self: Manifest): int =
 
 func steps*(self: Manifest): int =
   ## Number of EC groups in *protected* manifest
-  divUp(self.originalBlocksCount, self.ecK)
+  divUp(self.originalBlocksCount, self.ecK * self.interleave)
 
 func verify*(self: Manifest): ?!void =
   ## Check manifest correctness
@@ -144,6 +148,7 @@ proc `==`*(a, b: Manifest): bool =
     (if a.protected:
       (a.ecK == b.ecK) and
       (a.ecM == b.ecM) and
+      (a.interleave == b.interleave) and
       (a.originalManifest == b.originalManifest)
     else:
       true)
@@ -159,6 +164,7 @@ proc `$`*(self: Manifest): string =
     (if self.protected:
       ", ecK: " & $self.ecK &
       ", ecM: " & $self.ecM &
+      ", interleave: " & $self.interleave &
       ", originalManifest: " & $self.originalManifest
     else:
       "")
@@ -192,7 +198,8 @@ proc new*(
     manifest: Manifest,
     treeCid: Cid,
     datasetSize: NBytes,
-    ecK, ecM: int
+    ecK, ecM: int,
+    interleave: int
 ): Manifest =
   ## Create an erasure protected dataset from an
   ## unprotected one
@@ -206,6 +213,7 @@ proc new*(
     blockSize: manifest.blockSize,
     protected: true,
     ecK: ecK, ecM: ecM,
+    interleave: interleave,
     originalManifest: manifest)
 
 proc new*(
@@ -236,6 +244,7 @@ proc new*(
   codec: MultiCodec,
   ecK: int,
   ecM: int,
+  interleave: int,
   originalManifest: Manifest
 ): Manifest =
   Manifest(
@@ -248,5 +257,6 @@ proc new*(
     protected: true,
     ecK: ecK,
     ecM: ecM,
+    interleave: interleave,
     originalManifest: originalManifest
   )