diff --git a/eth.nimble b/eth.nimble
index d962cdd..b54b4f7 100644
--- a/eth.nimble
+++ b/eth.nimble
@@ -66,6 +66,9 @@ task test_trie, "Run trie tests":
 task test_db, "Run db tests":
   runTest("tests/db/all_tests")
 
+task test_ssz, "Run ssz tests":
+  runTest("tests/ssz/test_merkleization")
+
 task test, "Run all tests":
   for filename in [
       "test_bloom",
@@ -78,6 +81,7 @@ task test, "Run all tests":
   test_p2p_task()
   test_trie_task()
   test_db_task()
+  test_ssz_task()
 
 task test_discv5_full, "Run discovery v5 and its dependencies tests":
   test_keys_task()
diff --git a/eth/ssz/merkleization.nim b/eth/ssz/merkleization.nim
index 84f365d..8eaff32 100644
--- a/eth/ssz/merkleization.nim
+++ b/eth/ssz/merkleization.nim
@@ -362,10 +362,12 @@ template createMerkleizer*(totalElements: static Limit): SszMerkleizerImpl =
 
   const treeHeight = binaryTreeHeight totalElements
   var combinedChunks {.noInit.}: array[treeHeight, Digest]
-
+  
+  let topIndex = treeHeight - 1
+  
   SszMerkleizerImpl(
     combinedChunks: cast[ptr UncheckedArray[Digest]](addr combinedChunks),
-    topIndex: treeHeight - 1,
+    topIndex: if (topIndex < 0): 0 else: topIndex,
     totalChunks: 0)
 
 func getFinalHash*(merkleizer: SszMerkleizerImpl): Digest =
diff --git a/tests/ssz/test_merkleization.nim b/tests/ssz/test_merkleization.nim
new file mode 100644
index 0000000..4fc6433
--- /dev/null
+++ b/tests/ssz/test_merkleization.nim
@@ -0,0 +1,75 @@
+import 
+  sequtils, unittest,
+  nimcrypto/[hash, sha2], stew/endians2, 
+  ../eth/ssz/merkleization
+
+proc h(a, b: seq[byte]): seq[byte] =
+  var h: sha256
+  h.init()
+  h.update(a & b)
+  h.finish().data.toSeq()
+ 
+proc e(v: uint32): seq[byte] =
+  let elem: uint8 = 255
+  newSeqWith(28, elem) & v.toBytesLe().toSeq()
+
+proc z(i: int): seq[byte] =
+  zerohashes[i].data.toSeq()
+
+type TestData[limit: static int64] = object
+  count: uint32
+  expectedRoot: seq[byte]
+
+# only happy cases as our merkleizer will happy accept more chunks than limit
+# cases from - https://github.com/ethereum/eth2.0-specs/blob/dev/tests/core/pyspec/eth2spec/utils/test_merkle_minimal.py
+let cases = (
+  TestData[0](count: 0, expectedRoot: z(0)),
+  TestData[1](count: 0, expectedRoot: z(0)),
+  TestData[1](count: 1, expectedRoot: e(0)),
+
+  TestData[2](count: 0, expectedRoot: h(z(0), z(0))),
+  TestData[2](count: 1, expectedRoot: h(e(0), z(0))),
+  TestData[2](count: 2, expectedRoot: h(e(0), e(1))),
+
+  TestData[4](count: 0, expectedRoot: h(h(z(0), z(0)), z(1))),
+  TestData[4](count: 1, expectedRoot: h(h(e(0), z(0)), z(1))),
+  TestData[4](count: 2, expectedRoot: h(h(e(0), e(1)), z(1))),
+  TestData[4](count: 3, expectedRoot: h(h(e(0), e(1)), h(e(2), z(0)))),
+  TestData[4](count: 4, expectedRoot: h(h(e(0), e(1)), h(e(2), e(3)))),
+
+  TestData[8](count: 0, expectedRoot: h(h(h(z(0), z(0)), z(1)), z(2))),
+  TestData[8](count: 1, expectedRoot: h(h(h(e(0), z(0)), z(1)), z(2))),
+  TestData[8](count: 2, expectedRoot: h(h(h(e(0), e(1)), z(1)), z(2))),
+  TestData[8](count: 3, expectedRoot: h(h(h(e(0), e(1)), h(e(2), z(0))), z(2))),
+  TestData[8](count: 4, expectedRoot: h(h(h(e(0), e(1)), h(e(2), e(3))), z(2))),
+  TestData[8](count: 5, expectedRoot: h(h(h(e(0), e(1)), h(e(2), e(3))), h(h(e(4), z(0)), z(1)))),
+  TestData[8](count: 6, expectedRoot: h(h(h(e(0), e(1)), h(e(2), e(3))), h(h(e(4), e(5)), h(z(0), z(0))))),
+  TestData[8](count: 7, expectedRoot: h(h(h(e(0), e(1)), h(e(2), e(3))), h(h(e(4), e(5)), h(e(6), z(0))))),
+  TestData[8](count: 8, expectedRoot: h(h(h(e(0), e(1)), h(e(2), e(3))), h(h(e(4), e(5)), h(e(6), e(7))))),
+
+  TestData[16](count: 0, expectedRoot: h(h(h(h(z(0), z(0)), z(1)), z(2)), z(3))),
+  TestData[16](count: 1, expectedRoot: h(h(h(h(e(0), z(0)), z(1)), z(2)), z(3))),
+  TestData[16](count: 2, expectedRoot: h(h(h(h(e(0), e(1)), z(1)), z(2)), z(3))),
+  TestData[16](count: 3, expectedRoot: h(h(h(h(e(0), e(1)), h(e(2), z(0))), z(2)), z(3))),
+  TestData[16](count: 4, expectedRoot: h(h(h(h(e(0), e(1)), h(e(2), e(3))), z(2)), z(3))),
+  TestData[16](count: 5, expectedRoot: h(h(h(h(e(0), e(1)), h(e(2), e(3))), h(h(e(4), z(0)), z(1))), z(3))),
+  TestData[16](count: 6, expectedRoot: h(h(h(h(e(0), e(1)), h(e(2), e(3))), h(h(e(4), e(5)), h(z(0), z(0)))), z(3))),
+  TestData[16](count: 7, expectedRoot: h(h(h(h(e(0), e(1)), h(e(2), e(3))), h(h(e(4), e(5)), h(e(6), z(0)))), z(3))),
+  TestData[16](count: 8, expectedRoot: h(h(h(h(e(0), e(1)), h(e(2), e(3))), h(h(e(4), e(5)), h(e(6), e(7)))), z(3))),
+  TestData[16](count: 9, expectedRoot: h(h(h(h(e(0), e(1)), h(e(2), e(3))), h(h(e(4), e(5)), h(e(6), e(7)))), h(h(h(e(8), z(0)), z(1)), z(2))))
+)
+
+suite "Merkleization":
+  test "calculate correct root from provided chunks":
+    for testCase in cases.fields:
+      var merk = createMerkleizer(testCase.limit)
+      var i: uint32 = 0
+
+      while i < testCase.count:
+        let elem = e(i)
+        merk.addChunk(elem)
+        i = i + 1
+        
+      let calculatedRoot = merk.getFinalhash()
+
+      check calculatedRoot.data.toSeq() == testCase.expectedRoot