diff --git a/xfel_calibrate/calibrate.py b/xfel_calibrate/calibrate.py
index 717c205b944d305109053c897e14a011fa9e8c7b..ec2aa7835113a4451aef7f3245f75d9c862bc39d 100755
--- a/xfel_calibrate/calibrate.py
+++ b/xfel_calibrate/calibrate.py
@@ -758,7 +758,7 @@ def run():
                                   RuntimeWarning)
                 else:
                     df = {}
-                    exec (func, df)
+                    exec(func, df)
                     f = df[con_func]
                     import inspect
                     sig = inspect.signature(f)