diff --git a/reference/haskell/cli/testMain.hs b/reference/haskell/cli/testMain.hs
index 86ee6e6..0006830 100644
--- a/reference/haskell/cli/testMain.hs
+++ b/reference/haskell/cli/testMain.hs
@@ -15,8 +15,8 @@ smallDataSetCfg = MkDataSetCfg
   , _maxLog2NSlots = 5
   , _nSlots    = 5
   , _cellSize  = 128
-  , _blockSize = 1024
-  , _nCells    = 64
+  , _blockSize = 4096 -- 1024
+  , _nCells    = 256  -- 64
   , _nSamples  = 10
   , _dataSrc   = FakeData (Seed 12345)
   }
diff --git a/reference/nim/proof_input/src/dataset.nim b/reference/nim/proof_input/src/dataset.nim
index a0f4fd7..55c5e2e 100644
--- a/reference/nim/proof_input/src/dataset.nim
+++ b/reference/nim/proof_input/src/dataset.nim
@@ -19,6 +19,11 @@ const exDataSetCfg* =
                , dataSrc:  DataSource(kind: FakeData, seed: 12345)
                )
 
+const exGlobalCfg* = 
+  GlobalConfig( maxDepth:       16
+              , maxLog2NSlots:  5               
+              )
+
 #-------------------------------------------------------------------------------
 
 {.overflowChecks: off.}
diff --git a/reference/nim/proof_input/src/gen_input.nim b/reference/nim/proof_input/src/gen_input.nim
index cb45d00..5012efc 100644
--- a/reference/nim/proof_input/src/gen_input.nim
+++ b/reference/nim/proof_input/src/gen_input.nim
@@ -29,7 +29,7 @@ proc buildSlotTreeFull( slotCfg: SlotConfig ): (seq[MerkleTree], MerkleTree) =
 proc buildSlotTree( slotCfg: SlotConfig ): MerkleTree = 
   return buildSlotTreeFull(slotCfg)[1]
 
-proc generateProofInput*( dsetCfg: DataSetConfig, slotIdx: SlotIdx, entropy: Entropy ): SlotProofInput =
+proc generateProofInput*( globCfg: GlobalConfig, dsetCfg: DataSetConfig, slotIdx: SlotIdx, entropy: Entropy ): SlotProofInput =
   let nslots  = dsetCfg.nSlots
   let ncells  = dsetCfg.nCells
   let nblocks = ncells div cellsPerBlock
@@ -57,7 +57,7 @@ proc generateProofInput*( dsetCfg: DataSetConfig, slotIdx: SlotIdx, entropy: Ent
     let cellData  = slotLoadCellData( ourSlotCfg, cellIdx )
     let botProof  = merkleProof( blockTree , cellIdx mod cellsPerBlock )
     let topProof  = merkleProof( bigTree   , blockIdx )
-    let prf  = mergeMerkleProofs( botProof, topProof )
+    let prf       = padMerkleProof( mergeMerkleProofs( botProof, topProof ), globCfg.maxDepth )
     inputs.add( CellProofInput(cellData: cellData, merkleProof: prf) )
 
   return SlotProofInput( dataSetRoot: dsetRoot
@@ -66,7 +66,7 @@ proc generateProofInput*( dsetCfg: DataSetConfig, slotIdx: SlotIdx, entropy: Ent
                        , nSlots:      nslots
                        , slotIndex:   slotIdx
                        , slotRoot:    ourSlotRoot 
-                       , slotProof:   slotProof
+                       , slotProof:   padMerkleProof( slotProof, globCfg.maxLog2NSlots )
                        , proofInputs: inputs
                        )
 
diff --git a/reference/nim/proof_input/src/slot.nim b/reference/nim/proof_input/src/slot.nim
index 26e3388..94f8067 100644
--- a/reference/nim/proof_input/src/slot.nim
+++ b/reference/nim/proof_input/src/slot.nim
@@ -44,7 +44,7 @@ genFakeCell cfg (Seed seed) (CellIdx idx) = (mkCellData cfg $ B.pack list) where
   go cnt state = fromIntegral state'' : go (cnt-1) state'' where
     state' = state*(state + seed1)*(state + seed2) + state*(state `xor` 0x5a5a5a5a) + seed1*state + (seed2 + 17)
     state'' = mod state' 1698428844001831
-#]
+]#
 
 #-------------------------------------------------------------------------------
 
diff --git a/reference/nim/proof_input/src/testmain.nim b/reference/nim/proof_input/src/testmain.nim
index 1b34c75..9bdfe6b 100644
--- a/reference/nim/proof_input/src/testmain.nim
+++ b/reference/nim/proof_input/src/testmain.nim
@@ -50,8 +50,9 @@ when isMainModule:
 
   let slotIdx  = 3
   let fakedata = DataSource(kind: FakeData, seed: 12345)
-  let dsetcfg  = DataSetConfig( nCells: 256, nSlots: 5, nSamples: 5, dataSrc: fakedata)                      
+  let globcfg  = GlobalConfig( maxDepth: 16, maxLog2NSlots: 5)  
+  let dsetcfg  = DataSetConfig( nCells: 256, nSlots: 5, nSamples: 10, dataSrc: fakedata)                      
   let entropy  = toF( 1234567 )
-  let prfInput = generateProofInput(dsetcfg, slotIdx, entropy)
+  let prfInput = generateProofInput(globcfg, dsetcfg, slotIdx, entropy)
   exportProofInput( "json/foo.json" , prfInput )
 
diff --git a/reference/nim/proof_input/src/types.nim b/reference/nim/proof_input/src/types.nim
index c35ecb3..26ab33e 100644
--- a/reference/nim/proof_input/src/types.nim
+++ b/reference/nim/proof_input/src/types.nim
@@ -1,5 +1,6 @@
 
 import std/strutils
+import std/sequtils
 
 from constantine/math/io/io_fields import toDecimal
 
@@ -48,6 +49,18 @@ type
 
 #-------------------------------------------------------------------------------
 
+# the circuit expect merkle path of statically known length, so we need to pad them
+func padMerkleProof*( old: MerkleProof, newlen: int ): MerkleProof = 
+  let pad = newlen - old.merklePath.len
+  assert( pad >= 0 )
+  return MerkleProof( leafIndex:       old.leafIndex       
+                    , leafValue:       old.leafValue      
+                    , merklePath:      old.merklePath & repeat(zero,pad)
+                    , numberOfLeaves:  old.numberOfLeaves
+                    )
+
+#-------------------------------------------------------------------------------
+
 type 
 
   Seed*     = uint64
@@ -94,4 +107,8 @@ type
     nSamples* : int           # how many cells we sample
     dataSrc*  : DataSource    # slot data source
 
+  GlobalConfig* = object
+    maxDepth*      : int      # maximum depth of the big merkle tree (log2 of maximum numbers of cells per slot)
+    maxLog2NSlots* : int      # log2 of maximum number of slots per dataset
+
 #-------------------------------------------------------------------------------