diff --git a/R/getDegTx.R b/R/getDegTx.R
index 6d05575..9a65b17 100644
--- a/R/getDegTx.R
+++ b/R/getDegTx.R
@@ -37,16 +37,16 @@ getDegTx <- function(rse_tx, type = c("cell_component", "standard", "top1500"),
   
   type = arg_match(type)
   
+  # Validate rse_tx is a RangedSummarizedExperiment object
+  if (!is(rse_tx, "RangedSummarizedExperiment")) {
+    stop("'rse_tx' must be a RangedSummarizedExperiment object.", call. = FALSE)
+  }
+  
   # Check if assayname is in assayNames
   if (!assayname %in% assayNames(rse_tx)) {
     stop(sprintf("'%s' is not in assayNames(rse_tx).", assayname), call. = FALSE)
   }
   
-  # Validate rse_tx is a RangedSummarizedExperiment object
-  if (!is(rse_tx, "RangedSummarizedExperiment")) {
-    stop("rse_tx must be a RangedSummarizedExperiment object.", call. = FALSE)
-  }
-  
   # Check for validity and matching of tx names
   sig_transcripts = check_tx_names(rownames(rse_tx), sig_transcripts, 'rownames(rse_tx)', 'sig_transcripts')