diff --git a/R/as.ftmsData.R b/R/as.ftmsData.R
index a060d7c..d74f4c6 100644
--- a/R/as.ftmsData.R
+++ b/R/as.ftmsData.R
@@ -92,11 +92,11 @@ as.peakData <- function(e_data, f_data, e_meta, edata_cname, fdata_cname, mass_c
                         aroma_cname = NULL, modaroma_cname = NULL, dbe_cname = NULL, dbeo_cname = NULL, dbeai_cname = NULL,
                         elcomp_cname = NULL, instrument_type = "12T", data_scale = "abundance", check_rows = FALSE){
   
-
-  # check that e_data, f_data, and e_meta are data.frames #
-  if(!inherits(e_data, "data.frame")) stop("e_data must be of the class 'data.frame'")
-  if(!inherits(f_data, "data.frame")) stop("f_data must be of the class 'data.frame'")
-  if(!inherits(e_meta, "data.frame")) stop("e_meta must be of the class 'data.frame'")
+  
+  # make sure e_data, f_data, and e_meta are data.frames #
+  e_data <- as.data.frame(e_data)
+  f_data <- as.data.frame(f_data)
+  e_meta <- as.data.frame(e_meta)
   
   # check that the peak column exists in e_data and e_meta (if applicable) #
   if(!(edata_cname %in% names(e_data))) stop(paste("Peak/Mass column ", edata_cname," not found in e_data. See details of as.peakData for specifying column names.", sep = ""))