diff --git a/fieldExtraction/src/investment/postprocess.py b/fieldExtraction/src/investment/postprocess.py
index c365c2e..761bf91 100644
--- a/fieldExtraction/src/investment/postprocess.py
+++ b/fieldExtraction/src/investment/postprocess.py
@@ -186,7 +186,7 @@ def normalize_cpt_fields(value):
     Returns:
         list: A normalized list of string codes.
     """
-    if pd.isna(value):  # Handle NaN values
+    if value is None or (isinstance(value, float) and pd.isna(value)):  # Handle NaN values
         result = []
     elif isinstance(value, (list, tuple)):  # If already a list or tuple
         result = [str(v).strip() for v in value]
@@ -238,7 +238,6 @@ def postprocess(df):
                 df.loc[~df['DATE_VALID'], col] = df.loc[~df['DATE_VALID'], col].apply(reformat_to_yyyymmdd)
             if "CPT" in col:
                 df[col] = df[col].apply(normalize_cpt_fields)
-                df[col] = df[col].apply(lambda x: str(x) if isinstance(x, list) else x)
 
         # Normalize the 'AUTO_RENEWAL_TERM' column
         df["AUTO_RENEWAL_TERM"] = df["AUTO_RENEWAL_TERM"].apply(normalize_auto_renewal_term)