diff --git a/speedtest.py b/speedtest.py
index 60abf6f..b226014 100755
--- a/speedtest.py
+++ b/speedtest.py
@@ -1631,12 +1631,12 @@ def shell():
         raise SpeedtestCLIError('Cannot supply both --no-download and '
                                 '--no-upload')
 
-    if args.csv_header:
-        csv_header()
-
     if len(args.csv_delimiter) != 1:
         raise SpeedtestCLIError('--csv-delimiter must be a single character')
 
+    if args.csv_header:
+        csv_header(args.csv_delimiter)
+
     validate_optional_args(args)
 
     debug = getattr(args, 'debug', False)