diff --git a/src/hanoi_util.erl b/src/hanoi_util.erl
index ba8e4c0..c72ff50 100644
--- a/src/hanoi_util.erl
+++ b/src/hanoi_util.erl
@@ -62,7 +62,7 @@ encode_index_node(KVList, Compress) ->
                     OutData = [?SNAPPY_COMPRESSION|Snappied]
             end;
         gzip ->
-            GZipData = zlib:gzip(TermData);
+            GZipData = zlib:gzip(TermData),
             if byte_size(GZipData) > byte_size(TermData) ->
                     OutData = [?NO_COMPRESSION|TermData];
                true ->
diff --git a/src/hanoi_writer.erl b/src/hanoi_writer.erl
index 50e6bea..a02bea2 100644
--- a/src/hanoi_writer.erl
+++ b/src/hanoi_writer.erl
@@ -190,9 +190,9 @@ close_node(#state{nodes=[#node{ level=Level, members=NodeMembers }|RestNodes], c
     {ok, BlockData} = hanoi_util:encode_index_node(OrderedMembers, Compress),
     NodePos = State#state.index_file_pos,
 
-    BlockSize = byte_size(BlockData),
+    BlockSize = erlang:iolist_size(BlockData),
     Data = [ <<(BlockSize+2):32/unsigned, Level:16/unsigned>> | BlockData ],
-    DataSize = BlockData + 6,
+    DataSize = BlockSize + 6,
 
     ok = file:write(State#state.index_file, Data),