diff --git a/nitro/abi.nim b/nitro/abi.nim
index 2242b10..32eef1f 100644
--- a/nitro/abi.nim
+++ b/nitro/abi.nim
@@ -8,6 +8,7 @@ type
     bytes: seq[byte]
     tuples: seq[Tuple]
   Tuple = object
+    start: int
     postponed: seq[Split]
   Split = object
     head: Slice[int]
@@ -66,12 +67,12 @@ proc write*(writer: var AbiWriter, address: EthAddress) =
   writer.padleft(address.toArray)
 
 proc startTuple*(writer: var AbiWriter) =
-  writer.tuples.add(Tuple())
+  writer.tuples.add(Tuple(start: writer.bytes.len))
 
 proc finishTuple*(writer: var AbiWriter) =
   let tupl = writer.tuples.pop()
   for split in tupl.postponed:
-    let offset = writer.bytes.len - split.head.a
+    let offset = writer.bytes.len - tupl.start
     writer.bytes[split.head] = Abi.encode(offset.uint64)
     writer.bytes.add(split.tail)
 
diff --git a/tests/nitro/testAbi.nim b/tests/nitro/testAbi.nim
index 2da686c..0c02d95 100644
--- a/tests/nitro/testAbi.nim
+++ b/tests/nitro/testAbi.nim
@@ -80,9 +80,9 @@ suite "ABI encoding":
     writer.finishTuple()
     check writer.finish() ==
       Abi.encode(a) &
-      Abi.encode(3 * 32'u8) & # offset in tuple
+      Abi.encode(4 * 32'u8) & # offset from start of tuple
       Abi.encode(c) &
-      Abi.encode(3 * 32'u8) & # offset in tuple
+      Abi.encode(6 * 32'u8) & # offset from start of tuple
       Abi.encode(b) &
       Abi.encode(d)
 
@@ -102,9 +102,9 @@ suite "ABI encoding":
     writer.finishTuple()
     check writer.finish() ==
       Abi.encode(a) &
-      Abi.encode(5 * 32'u8) & # offset in tuple
+      Abi.encode(6 * 32'u8) & # offset from start of tuple
       Abi.encode(c) &
-      Abi.encode(1 * 32'u8) & # offset in tuple
+      Abi.encode(2 * 32'u8) & # offset from start of tuple
       Abi.encode(d) &
       Abi.encode(b)
 
@@ -136,7 +136,7 @@ suite "ABI encoding":
     writer.write(s)
     writer.finishTuple()
     check writer.finish() ==
-      Abi.encode(32'u8) & # offset in tuple
+      Abi.encode(32'u8) & # offset from start of tuple
       Abi.encode(s)
 
   test "encodes array of static elements as static element":
@@ -154,7 +154,7 @@ suite "ABI encoding":
     writer.write(a)
     writer.finishTuple()
     check writer.finish() ==
-      Abi.encode(32'u8) & # offset in tuple
+      Abi.encode(32'u8) & # offset from start of tuple
       Abi.encode(a)
 
 # https://medium.com/b2expand/abi-encoding-explanation-4f470927092d