diff --git a/rdt/transformers/categorical.py b/rdt/transformers/categorical.py
index 97bcf71fb..b0b0b1636 100644
--- a/rdt/transformers/categorical.py
+++ b/rdt/transformers/categorical.py
@@ -89,6 +89,7 @@ def _get_intervals(data):
             dict:
                 intervals for each categorical value (start, end).
         """
+        data = data.fillna(np.nan)
         frequencies = data.value_counts(dropna=False)
 
         start = 0