diff --git a/storage/google/cloud/storage/bucket.py b/storage/google/cloud/storage/bucket.py
index 1163de8f8452..9f235d309c85 100644
--- a/storage/google/cloud/storage/bucket.py
+++ b/storage/google/cloud/storage/bucket.py
@@ -1352,8 +1352,9 @@ 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 0b7fa8762a58..d9295991fe0f 100644
--- a/storage/tests/unit/test_bucket.py
+++ b/storage/tests/unit/test_bucket.py
@@ -1597,13 +1597,14 @@ 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