--as-cran error

Dear List,

While using the --as-cran option for checking one of my packages:

R CMD check --as-cran hydroGOF_0.3-3.tar.gz


I got the following error message:

pkgname <- "hydroGOF"
 > source(file.path(R.home("share"), "R", "examples-header.R"))
 > options(warn = 1)
 > library('hydroGOF')
Error in loadNamespace(i[[1L]], c(lib.loc, .libPaths())) :
   there is no package called ?class?

However, I don't get any error message when the checking is done without 
the --as-cran option.

Could somebody give me a hint about how to solve this error before 
submission to CRAN ?


sessionInfo()
R version 2.15.0 (2012-03-30)
Platform: x86_64-redhat-linux-gnu (64-bit)

locale:
  [1] LC_CTYPE=en_GB.utf8       LC_NUMERIC=C
  [3] LC_TIME=en_GB.utf8        LC_COLLATE=en_GB.utf8
  [5] LC_MONETARY=en_GB.utf8    LC_MESSAGES=en_GB.utf8
  [7] LC_PAPER=C                LC_NAME=C
  [9] LC_ADDRESS=C              LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_GB.utf8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base


Thanks in advance,

Mauricio Zambrano-Bigiarini

====================================================
Water Resources Unit
Institute for Environment and Sustainability (IES)
Joint Research Centre (JRC), European Commission
webinfo    : http://floods.jrc.ec.europa.eu/
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and may not in any circumstances be regarded as sta-
ting an official position of the European Commission"
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