diff --git a/R/estimate_size_factors.R b/R/estimate_size_factors.R
index b9e56c4..26e82f2 100644
--- a/R/estimate_size_factors.R
+++ b/R/estimate_size_factors.R
@@ -83,7 +83,7 @@ combine_size_factors_and_offset <- function(offset, size_factors, Y, verbose = F
   if(is.matrix(offset)){
     stopifnot(dim(offset) == c(n_genes, n_samples))
     offset_matrix <- offset
-  }else if(is(offset, "HDF5Matrix")){
+  }else if(is(offset, "HDF5Matrix") || is(offset, "DelayedArray")){
     stopifnot(dim(offset) == c(n_genes, n_samples))
     stopifnot(make_offset_hdf5_mat)
     offset_matrix <- offset