diff --git a/hw-xml.cabal b/hw-xml.cabal
--- a/hw-xml.cabal
+++ b/hw-xml.cabal
@@ -1,7 +1,7 @@
 cabal-version: 2.2
 
 name:                 hw-xml
-version:              0.4.0.5
+version:              0.4.0.6
 synopsis:             XML parser based on succinct data structures.
 description:          XML parser based on succinct data structures. Please see README.md
 category:             Data, XML, Succinct Data Structures, Data Structures
diff --git a/src/HaskellWorks/Data/Xml/Succinct/Cursor/Create.hs b/src/HaskellWorks/Data/Xml/Succinct/Cursor/Create.hs
--- a/src/HaskellWorks/Data/Xml/Succinct/Cursor/Create.hs
+++ b/src/HaskellWorks/Data/Xml/Succinct/Cursor/Create.hs
@@ -23,8 +23,10 @@
   , balancedParens  = SimpleBalancedParens bp
   , cursorRank      = 1
   }
-  where blankedXml = bsToBlankedXml bs
-        (ib, bp) = construct64UnzipN (BS.length bs) (I.toIbBp64 blankedXml)
+  where blankedXml  = bsToBlankedXml bs
+        bsLen       = BS.length bs
+        idxLen      = (bsLen + 7) `div` 8
+        (ib, bp)    = construct64UnzipN idxLen (I.toIbBp64 blankedXml)
 
 byteStringAsFastCursor :: BS.ByteString -> FastCursor
 byteStringAsFastCursor bs = XmlCursor bs ibCsPoppy rangeMinMax r