[R-pkg-devel] Error creating union class: object ‘.__C__compMatrix’ not found

Hi,

I tried to solve the issue in multiple ways, but I keep getting an installation error when running R CMD check, although the package installs fine with R CMD INSTALL:

Error: package ?Matrix? required by ?NMF? could not be found

I clearly have the package Matrix installed and up-to-date.
I tried with/without Matrix in Depends, with/without importing it all in the NAMESPACE.
Do I need to have a statement like this in the NAMESPACE:

importClassesFrom(Matrix,mMatrix)


The class appears not to be exported.
Puzzled.

Thank you.