diff --git a/storage/google/cloud/storage/bucket.py b/storage/google/cloud/storage/bucket.py
index 9829f3b6d7c9..419063f7910a 100644
--- a/storage/google/cloud/storage/bucket.py
+++ b/storage/google/cloud/storage/bucket.py
@@ -1347,8 +1347,9 @@ def retention_period(self, value):
         """
         policy = self._properties.setdefault('retentionPolicy', {})
         if value is not None:
-            value = str(value)
-        policy['retentionPeriod'] = value
+            policy['retentionPeriod'] = str(value)
+        else:
+            policy = None
         self._patch_property('retentionPolicy', policy)
 
     @property
diff --git a/storage/tests/unit/test_bucket.py b/storage/tests/unit/test_bucket.py
index 8ee3fafd8239..abb7488c6f7a 100644
--- a/storage/tests/unit/test_bucket.py
+++ b/storage/tests/unit/test_bucket.py
@@ -1573,13 +1573,14 @@ def test_retention_period_getter(self):
     def test_retention_period_setter_w_none(self):
         period = 86400 * 100  # 100 days
         bucket = self._make_one()
-        policy = bucket._properties['retentionPolicy'] = {}
-        policy['retentionPeriod'] = period
+        bucket._properties['retentionPolicy'] = {
+            'retentionPeriod': period,
+        }
 
         bucket.retention_period = None
 
         self.assertIsNone(
-            bucket._properties['retentionPolicy']['retentionPeriod'])
+            bucket._properties['retentionPolicy'])
 
     def test_retention_period_setter_w_int(self):
         period = 86400 * 100  # 100 days