diff --git a/monetio/obs/openaq.py b/monetio/obs/openaq.py
index da6b1e7b..41c68661 100644
--- a/monetio/obs/openaq.py
+++ b/monetio/obs/openaq.py
@@ -4,11 +4,14 @@
 https://openaq-fetches.s3.amazonaws.com/index.html
 """
 import json
+import sys
 import warnings
 
 import pandas as pd
 from numpy import NaN
 
+_PY39_PLUS = sys.version_info >= (3, 9)
+
 _URL_CAP_RANDOM_SAMPLE = False  # if false, take from end of list
 _URL_CAP = None  # set to int to limit number of files loaded for testing
 
@@ -492,8 +495,15 @@ def add_data(self, dates, *, num_workers=1, wide_fmt=True):
         # with different location names.
         # Occasionally, there are rows that appear to actual duplicates
         # (e.g. all same except one col is null in one or something)
-        def do_hash(b):
-            return hashlib.sha1(b, usedforsecurity=False).hexdigest()
+        if _PY39_PLUS:
+
+            def do_hash(b):
+                return hashlib.sha1(b, usedforsecurity=False).hexdigest()
+
+        else:
+
+            def do_hash(b):
+                return hashlib.sha1(b).hexdigest()
 
         # to_hash = df.latitude.astype(str) + " " + df.longitude.astype(str)
         to_hash = df.location + " " + df.latitude.astype(str) + " " + df.longitude.astype(str)