diff --git a/src/dxtbx/format/FormatNXmxEigerFilewriter.py b/src/dxtbx/format/FormatNXmxEigerFilewriter.py
index a3e73c145..fbfde2929 100644
--- a/src/dxtbx/format/FormatNXmxEigerFilewriter.py
+++ b/src/dxtbx/format/FormatNXmxEigerFilewriter.py
@@ -52,7 +52,9 @@ def _get_nxmx(self, fh: h5py.File):
         # data_size is reversed - we should probably be more specific in when
         # we do this, i.e. check data_size is in a list of known reversed
         # values
-        known_safe = [(1082,1035),]
+        known_safe = [
+            (1082, 1035),
+        ]
         for module in nxdetector.modules:
             if not tuple(module.data_size) in known_safe:
                 module.data_size = module.data_size[::-1]