diff --git a/plot_single_transmission_EM9190.py b/plot_single_transmission_EM9190.py
index 14b8172..56ea2b2 100755
--- a/plot_single_transmission_EM9190.py
+++ b/plot_single_transmission_EM9190.py
@@ -28,6 +28,13 @@ tex_fonts = {
 #plt.rcParams.update(tex_fonts)
 
 
+def convert_cellid(value):
+    if isinstance(value, str):
+        return int(value.split(" ")[-1].replace("(", "").replace(")", ""))
+    else:
+        return int(-1)
+    
+
 if __name__ == "__main__":
     parser = ArgumentParser()
     parser.add_argument("-s", "--serial_file", required=True, help="Serial csv file.")
@@ -91,7 +98,7 @@ if __name__ == "__main__":
         #transmission_df = transmission_df.filter(["goodput", "datetime", "ack_rtt", "goodput_rolling", "snd_cwnd"])
 
         # read serial csv
-        serial_df = pd.read_csv(args.serial_file, dtype=dict(Cell_ID=str),)
+        serial_df = pd.read_csv(args.serial_file, converters={"Cell_ID": convert_cellid})
         serial_df["datetime"] = pd.to_datetime(serial_df["datetime"]) - pd.Timedelta(hours=1)
         serial_df = serial_df.set_index("datetime")
         serial_df.index = pd.to_datetime(serial_df.index)
@@ -99,8 +106,8 @@ if __name__ == "__main__":
 
         print(serial_df["Cell_ID"])
 
-        serial_df["Cell_ID"] = serial_df["Cell_ID"].apply(
-            lambda x: int(x.split(" ")[-1].replace("(", "").replace(")", "")))
+        #serial_df["Cell_ID"] = serial_df["Cell_ID"].apply(
+        #    lambda x: int(x.split(" ")[-1].replace("(", "").replace(")", "")))
 
         transmission_df = pd.merge_asof(
             transmission_df,