diff --git a/fsl/scripts/fsl_apply_x5.py b/fsl/scripts/fsl_apply_x5.py
index ed535ea96a6082213939aa9d9130e7b9dea319e5..b64ce113bf4b3f8f5f661fa0b5d18fbd1e461326 100644
--- a/fsl/scripts/fsl_apply_x5.py
+++ b/fsl/scripts/fsl_apply_x5.py
@@ -20,7 +20,7 @@ import fsl.utils.image.resample as resample
 import fsl.data.image           as fslimage
 
 
-def parseArgs(args=None):
+def parseArgs(args):
     """Parses command-line arguments.
 
     :arg args: Sequence of command-line arguments. If ``None``, ``sys.argv``
@@ -121,6 +121,15 @@ def main(args=None):
     type.
     """
 
+    if args is None:
+        args = sys.argv[1:]
+
+    print()
+    print('Warning: this version of fsl_apply_x5 is a development release. '
+          'Interface, behaviour, and input/output formats of future versions '
+          'may differ from this version.')
+    print()
+
     args = parseArgs(args)
 
     if x5.inferType(args.xform) == 'linear':
diff --git a/fsl/scripts/fsl_convert_x5.py b/fsl/scripts/fsl_convert_x5.py
index f7bf84981a15757ee493224d56ef6213d043ccb4..a4f22ab0764608e1952898cc45ae3f5066fe1086 100644
--- a/fsl/scripts/fsl_convert_x5.py
+++ b/fsl/scripts/fsl_convert_x5.py
@@ -182,6 +182,12 @@ def main(args=None):
     if args is None:
         args = sys.argv[1:]
 
+    print()
+    print('Warning: this version of fsl_convert_x5 is a development release. '
+          'Interface, behaviour, and input/output formats of future versions '
+          'may differ from this version.')
+    print()
+
     args = parseArgs(args)
 
     if   args.ctype == 'flirt': doFlirt(args)