diff --git a/downloads-generation/models_class1_pan_variants/reassign_mass_spec_training_data.py b/downloads-generation/models_class1_pan_variants/reassign_mass_spec_training_data.py
index 24b4158779e4ccf10d59c9e400232cacfe379eca..7e1d19c0126c49ad0d14d53bddefcde74386e285 100644
--- a/downloads-generation/models_class1_pan_variants/reassign_mass_spec_training_data.py
+++ b/downloads-generation/models_class1_pan_variants/reassign_mass_spec_training_data.py
@@ -32,7 +32,7 @@ def go(args):
 
     if args.ms_only:
         print("Filtering to MS only")
-        df = df.loc[df.measurement_kind == "mass_spec"]
+        df = df.loc[df.measurement_kind == "mass_spec"].copy()
 
     if args.set_measurement_value:
         indexer = df.measurement_kind == "mass_spec"