diff --git a/R/load_matrix.R b/R/load_matrix.R
index 9a8dafcb3839b88bd803de3bed552afe94c71bf9..2487c61d82f59c4e9ce2808389a9a02a34729852 100644
--- a/R/load_matrix.R
+++ b/R/load_matrix.R
@@ -36,6 +36,7 @@ load_matrix <- function(design_table, path, my_formula) {
         path = path
     ))
     design_table$count_files <- selected_files
+    design_table <- design_table[, !names(design_table) %in% c("prefix")]
     sample_table <- dplyr::rename(design_table,
         sampleName = sample,
         fileName = count_files
@@ -49,6 +50,7 @@ load_matrix <- function(design_table, path, my_formula) {
         sample_table[[my_col]] <- as.factor(sample_table[[my_col]])
     }
     sample_table <- sample_table[, c("sampleName", "fileName", "condition")]
+    sample_table$condition <- as.factor(sample_table$condition)
     dds_input <- DESeq2::DESeqDataSetFromHTSeqCount(
         sampleTable = as.data.frame(sample_table),
         directory = ".",