I'm working with the R package lidR to process point clouds. I have a raster with 4 coarse land cover classes and the corresponding tile with the LiDAR data in las format (both in the same coordinate system). Now I want to attach the land cover classes to the point cloud with the lasmergespatial tool from the lidR package.

#import las
mylas<-readLAS(files="xyz.las", select = "xyzia", filter = "")


#import raster as rasster (not as stack)
landcover<-raster("LC_raster.tif")

#classify las with raster
class_las<-lasmergespatial(mylas, landcover, attribute = "class")

So basically I don't get errors but the attribute class in the new created las file is empty with NA. What might be a problem?