diff --git a/main.py b/main.py
index 0f922ee..2093118 100755
--- a/main.py
+++ b/main.py
@@ -71,7 +71,8 @@ if args.subparser_name == 'rank':
 else:
     dates = chain.from_iterable(v for v in entries.values())
     timestamps = list(d.timestamp() for d in dates)
-    num_buckets = (max_date - min_date).total_seconds() / (args.bucket_size * 3600)
+    bucket_size = max(args.bucket_size, 1)
+    num_buckets = (max_date - min_date).total_seconds() / (bucket_size * 3600)
     num_buckets = max(1, int(num_buckets))
     counts, bin_edges = np.histogram(timestamps, bins=num_buckets)
     fig = tpl.figure()