diff --git a/aif360/algorithms/preprocessing/optim_preproc_helpers/data_preproc_functions.py b/aif360/algorithms/preprocessing/optim_preproc_helpers/data_preproc_functions.py
index 11e0b296..3d3fd278 100644
--- a/aif360/algorithms/preprocessing/optim_preproc_helpers/data_preproc_functions.py
+++ b/aif360/algorithms/preprocessing/optim_preproc_helpers/data_preproc_functions.py
@@ -10,7 +10,7 @@ def custom_preprocessing(df):
         """
 
         # Group age by decade
-        df['Age (decade)'] = df['age'].apply(lambda x: x//10*10)
+        df['Age (decade)'] = df['age'].astype(int).apply(lambda x: x//10*10)
         # df['Age (decade)'] = df['age'].apply(lambda x: np.floor(x/10.0)*10.0)
 
         def group_edu(x):