"Next" in quantmod

Not sure is this is a bug, or a feature, or just a brain-cramp on my end:

require(quantmod)

Loading required package: quantmod
Loading required package: xts
Loading required package: zoo

Attaching package: 'zoo'

        The following object(s) are masked from package:base :

         as.Date.numeric

Loading required package: Defaults
quantmod: Quantitative Financial Modelling Framework

Version 0.3-7, Revision 461
http://www.quantmod.com

getSymbols("CSCO")

[1] "CSCO"

head(Lag(Cl(CSCO)))

Lag.1
2007-01-03    NA
2007-01-04 27.73
2007-01-05 28.46
2007-01-08 28.47
2007-01-09 28.63
2007-01-10 28.47

head(Next(Cl(CSCO)))                                <--------------

Error in `[.xts`(x, -(0:k), ) :
  only zeros may be mixed with negative subscripts

R.version.string