diff --git a/remotefilelog/repack.py b/remotefilelog/repack.py
--- a/remotefilelog/repack.py
+++ b/remotefilelog/repack.py
@@ -476,13 +476,18 @@
                 if deltabase != nullid:
                     deltabasetext = self.data.get(filename, deltabase)
                     original = self.data.get(filename, node)
+                    size = len(original)
                     delta = mdiff.textdiff(deltabasetext, original)
                 else:
                     delta = self.data.get(filename, node)
+                    size = len(delta)
 
                 # TODO: don't use the delta if it's larger than the fulltext
                 # TODO: don't use the delta if the chain is already long
                 meta = self.data.getmeta(filename, node)
+                from remotefilelog.constants import METAKEYSIZE
+                if METAKEYSIZE not in meta:
+                    meta[METAKEYSIZE] = size
                 target.add(filename, node, deltabase, delta, meta)
 
                 entries[node].datarepacked = True
diff --git a/tests/test-remotefilelog-repack-fast.t b/tests/test-remotefilelog-repack-fast.t
--- a/tests/test-remotefilelog-repack-fast.t
+++ b/tests/test-remotefilelog-repack-fast.t
@@ -306,7 +306,7 @@
   $ hg repack --incremental
   $ ls_l $TESTTMP/hgcache/master/packs/ | grep datapack
   -r--r--r--      59 5b7dec902026f0cddb0ef8acb62f27b5698494d4.datapack
-  -r--r--r--     213 f3c56163b762b2931865bbbb1250b4fae09e782c.datapack
+  -r--r--r--     225 8fe685c56f6f7edf550bfcec74eeecc5f3c2ba15.datapack
   $ ls_l $TESTTMP/hgcache/master/packs/ | grep histpack
   -r--r--r--     336 094b530486dad4427a0faf6bcbc031571b99ca24.histpack
 
@@ -314,7 +314,7 @@
   $ hg repack --incremental
   $ ls_l $TESTTMP/hgcache/master/packs/ | grep datapack
   -r--r--r--      59 5b7dec902026f0cddb0ef8acb62f27b5698494d4.datapack
-  -r--r--r--     213 f3c56163b762b2931865bbbb1250b4fae09e782c.datapack
+  -r--r--r--     225 8fe685c56f6f7edf550bfcec74eeecc5f3c2ba15.datapack
   $ ls_l $TESTTMP/hgcache/master/packs/ | grep histpack
   -r--r--r--     336 094b530486dad4427a0faf6bcbc031571b99ca24.histpack
 
@@ -352,7 +352,7 @@
   $ hg debugwaitonrepack >/dev/null 2>&1
   $ ls_l $TESTTMP/hgcache/master/packs/ | grep datapack
   -r--r--r--      59 5b7dec902026f0cddb0ef8acb62f27b5698494d4.datapack
-  -r--r--r--     213 f3c56163b762b2931865bbbb1250b4fae09e782c.datapack
+  -r--r--r--     225 8fe685c56f6f7edf550bfcec74eeecc5f3c2ba15.datapack
   $ ls_l $TESTTMP/hgcache/master/packs/ | grep histpack
   -r--r--r--     336 094b530486dad4427a0faf6bcbc031571b99ca24.histpack
 
diff --git a/tests/test-remotefilelog-repack.t b/tests/test-remotefilelog-repack.t
--- a/tests/test-remotefilelog-repack.t
+++ b/tests/test-remotefilelog-repack.t
@@ -301,7 +301,7 @@
   $ hg repack --incremental
   $ ls_l $TESTTMP/hgcache/master/packs/ | grep datapack
   -r--r--r--      59 5b7dec902026f0cddb0ef8acb62f27b5698494d4.datapack
-  -r--r--r--     213 f3c56163b762b2931865bbbb1250b4fae09e782c.datapack
+  -r--r--r--     225 8fe685c56f6f7edf550bfcec74eeecc5f3c2ba15.datapack
   $ ls_l $TESTTMP/hgcache/master/packs/ | grep histpack
   -r--r--r--     336 094b530486dad4427a0faf6bcbc031571b99ca24.histpack
 
@@ -309,7 +309,7 @@
   $ hg repack --incremental
   $ ls_l $TESTTMP/hgcache/master/packs/ | grep datapack
   -r--r--r--      59 5b7dec902026f0cddb0ef8acb62f27b5698494d4.datapack
-  -r--r--r--     213 f3c56163b762b2931865bbbb1250b4fae09e782c.datapack
+  -r--r--r--     225 8fe685c56f6f7edf550bfcec74eeecc5f3c2ba15.datapack
   $ ls_l $TESTTMP/hgcache/master/packs/ | grep histpack
   -r--r--r--     336 094b530486dad4427a0faf6bcbc031571b99ca24.histpack
 
@@ -347,7 +347,7 @@
   $ hg debugwaitonrepack >/dev/null 2>&1
   $ ls_l $TESTTMP/hgcache/master/packs/ | grep datapack
   -r--r--r--      59 5b7dec902026f0cddb0ef8acb62f27b5698494d4.datapack
-  -r--r--r--     213 f3c56163b762b2931865bbbb1250b4fae09e782c.datapack
+  -r--r--r--     225 8fe685c56f6f7edf550bfcec74eeecc5f3c2ba15.datapack
   $ ls_l $TESTTMP/hgcache/master/packs/ | grep histpack
   -r--r--r--     336 094b530486dad4427a0faf6bcbc031571b99ca24.histpack
 
@@ -387,11 +387,11 @@
   
   x
   Node          Delta Base    Delta Length  Blob Size
-  1bb2e6237e03  000000000000  8             (missing)
-  d4a3ed9310e5  1bb2e6237e03  12            (missing)
-  aee31534993a  000000000000  4             (missing)
-  1406e7411862  aee31534993a  12            (missing)
+  1bb2e6237e03  000000000000  8             8
+  d4a3ed9310e5  1bb2e6237e03  12            6
+  aee31534993a  000000000000  4             4
+  1406e7411862  aee31534993a  12            2
   
   y
   Node          Delta Base    Delta Length  Blob Size
-  577959738234  000000000000  8             (missing)
+  577959738234  000000000000  8             8
diff --git a/tests/test-treemanifest-repack.t b/tests/test-treemanifest-repack.t
--- a/tests/test-treemanifest-repack.t
+++ b/tests/test-treemanifest-repack.t
@@ -81,19 +81,19 @@
   $ hg repack
 
   $ ls_l $CACHEDIR/master/packs/manifests | grep pack
+  -r--r--r--     339 56e8c6f0ca2a324b8b5ca1a2730323a1b4d0793a.datapack
   -r--r--r--     262 7535b6084226436bbdff33043969e7fa963e8428.histpack
-  -r--r--r--     327 be1a1ae9828d9bd09ab8ba765db358f99fd09ea7.datapack
 
   $ hg debugdatapack $CACHEDIR/master/packs/manifests/*.datapack
   
   
   Node          Delta Base    Delta Length  Blob Size
-  1832e0765de9  000000000000  89            (missing)
-  a0c8bcbbb45c  1832e0765de9  12            (missing)
+  1832e0765de9  000000000000  89            89
+  a0c8bcbbb45c  1832e0765de9  12            43
   
   dir
   Node          Delta Base    Delta Length  Blob Size
-  23226e7a252c  000000000000  43            (missing)
+  23226e7a252c  000000000000  43            43
 
   $ hg debughistorypack $CACHEDIR/master/packs/manifests/*.histpack
   
@@ -115,32 +115,32 @@
   -r--r--r--     146 cffef142da32f3e52c1779490e5d0ddac5f9b82b.datapack
   $ hg repack
   $ ls_l .hg/store/packs/manifests | grep datapack
-  -r--r--r--     374 201094db51b761cd78352c055b3135178aadfec5.datapack
+  -r--r--r--     386 d15c09a9a5a13bb689bd9764455a415a20dc885e.datapack
 
 # Test incremental repacking of trees
   $ echo b >> dir/b && hg commit -Aqm 'modify dir/b'
   $ echo b >> dir/b && hg commit -Aqm 'modify dir/b'
   $ ls_l .hg/store/packs/manifests | grep datapack
-  -r--r--r--     374 201094db51b761cd78352c055b3135178aadfec5.datapack
   -r--r--r--     248 21501384df03b8489b366c5218be639fa08830e4.datapack
+  -r--r--r--     386 d15c09a9a5a13bb689bd9764455a415a20dc885e.datapack
   -r--r--r--     248 d7e689a91ac63385be120a118af9ce8663748f28.datapack
 
 - repack incremental does nothing here because there are so few packs
   $ hg repack --incremental --config remotefilelog.data.generations=300,200 --config remotefilelog.data.repacksizelimit=300
   $ ls_l .hg/store/packs/manifests | grep datapack
-  -r--r--r--     374 201094db51b761cd78352c055b3135178aadfec5.datapack
   -r--r--r--     248 21501384df03b8489b366c5218be639fa08830e4.datapack
+  -r--r--r--     386 d15c09a9a5a13bb689bd9764455a415a20dc885e.datapack
   -r--r--r--     248 d7e689a91ac63385be120a118af9ce8663748f28.datapack
 
   $ echo b >> dir/b && hg commit -Aqm 'modify dir/b'
   $ echo b >> dir/b && hg commit -Aqm 'modify dir/b'
   $ echo b >> dir/b && hg commit -Aqm 'modify dir/b'
   $ ls_l .hg/store/packs/manifests | grep datapack
-  -r--r--r--     374 201094db51b761cd78352c055b3135178aadfec5.datapack
   -r--r--r--     248 21501384df03b8489b366c5218be639fa08830e4.datapack
   -r--r--r--     248 347263bf1efbdb5bf7e1d1565b6b504073fb9093.datapack
   -r--r--r--     248 544a3b46a61732209116ae50847ec333b75e3765.datapack
   -r--r--r--     248 863908ef8149261ab0d891c2344d8e8766c39441.datapack
+  -r--r--r--     386 d15c09a9a5a13bb689bd9764455a415a20dc885e.datapack
   -r--r--r--     248 d7e689a91ac63385be120a118af9ce8663748f28.datapack
   $ cd .hg/store/packs/manifests
   $ cp d7e689a91ac63385be120a118af9ce8663748f28.datapack x7e689a91ac63385be120a118af9ce8663748f28.datapack