diff --git a/core/config/schema/core.data_types.schema.yml b/core/config/schema/core.data_types.schema.yml
index ed775d8..0c9ad70 100644
--- a/core/config/schema/core.data_types.schema.yml
+++ b/core/config/schema/core.data_types.schema.yml
@@ -308,11 +308,6 @@ block_settings:
     provider:
       type: string
       label: 'Provider'
-    context_mapping:
-      type: sequence
-      label: 'Context assignments'
-      sequence:
-        - type: string
 
 condition.plugin:
   type: mapping
diff --git a/core/modules/aggregator/config/schema/aggregator.schema.yml b/core/modules/aggregator/config/schema/aggregator.schema.yml
index db7c93a6..a0a3d4a 100644
--- a/core/modules/aggregator/config/schema/aggregator.schema.yml
+++ b/core/modules/aggregator/config/schema/aggregator.schema.yml
@@ -44,6 +44,10 @@ block.settings.aggregator_feed_block:
     block_count:
       type: integer
       label: 'Block count'
-    feed:
-      type: string
-      label: 'Feed'
+    context_mapping:
+      type: mapping
+      label: 'Context assignments'
+      mapping:
+        feed:
+          type: string
+          label: 'Feed'
diff --git a/core/modules/aggregator/src/Plugin/Block/AggregatorFeedBlock.php b/core/modules/aggregator/src/Plugin/Block/AggregatorFeedBlock.php
index 62d1344..4fca9c9 100644
--- a/core/modules/aggregator/src/Plugin/Block/AggregatorFeedBlock.php
+++ b/core/modules/aggregator/src/Plugin/Block/AggregatorFeedBlock.php
@@ -87,7 +87,6 @@ public function defaultConfiguration() {
     // By default, the block will contain 10 feed items.
     return array(
       'block_count' => 10,
-      'feed' => NULL,
       // Modify the default max age for the 'Aggregator Feed' blocks:
       // modifications made to feeds or feed items will automatically invalidate
       // corresponding cache tags, therefore allowing us to cache these blocks
@@ -125,7 +124,6 @@ public function blockForm($form, FormStateInterface $form_state) {
    */
   public function blockSubmit($form, FormStateInterface $form_state) {
     $this->configuration['block_count'] = $form_state->getValue('block_count');
-    $this->configuration['feed'] = $form_state->getValue('feed');
   }
 
   /**