diff --git a/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
index 51b7c1aa3a..44b560c242 100644
--- a/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
+++ b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
@@ -434,9 +434,9 @@ public function addField($table, $field, $spec, $keys_new = []) {
         ->execute();
     }
     if (isset($spec['initial_from_field'])) {
-      if (is_array($spec['initial_from_field'])) {
-        $expression = 'COALESCE(' . $spec['initial_from_field']['field_name'] . ', :default_initial_value)';
-        $arguments = [':default_initial_value' => $spec['initial_from_field']['default_value']];
+      if (isset($spec['initial'])) {
+        $expression = 'COALESCE(' . $spec['initial_from_field'] . ', :default_initial_value)';
+        $arguments = [':default_initial_value' => $spec['initial']];
       }
       else {
         $expression = $spec['initial_from_field'];
diff --git a/core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php b/core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php
index 3d8019c23e..58c6587661 100644
--- a/core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php
+++ b/core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php
@@ -568,9 +568,9 @@ public function addField($table, $field, $spec, $new_keys = []) {
         ->execute();
     }
     if (isset($spec['initial_from_field'])) {
-      if (is_array($spec['initial_from_field'])) {
-        $expression = 'COALESCE(' . $spec['initial_from_field']['field_name'] . ', :default_initial_value)';
-        $arguments = [':default_initial_value' => $spec['initial_from_field']['default_value']];
+      if (isset($spec['initial'])) {
+        $expression = 'COALESCE(' . $spec['initial_from_field'] . ', :default_initial_value)';
+        $arguments = [':default_initial_value' => $spec['initial']];
       }
       else {
         $expression = $spec['initial_from_field'];
diff --git a/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php b/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php
index 40222e0741..8c0ce54dc4 100644
--- a/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php
+++ b/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php
@@ -333,9 +333,9 @@ public function addField($table, $field, $specification, $keys_new = []) {
           ->execute();
       }
       if (isset($specification['initial_from_field'])) {
-        if (is_array($specification['initial_from_field'])) {
-          $expression = 'COALESCE(' . $specification['initial_from_field']['field_name'] . ', :default_initial_value)';
-          $arguments = [':default_initial_value' => $specification['initial_from_field']['default_value']];
+        if (isset($specification['initial'])) {
+          $expression = 'COALESCE(' . $specification['initial_from_field'] . ', :default_initial_value)';
+          $arguments = [':default_initial_value' => $specification['initial']];
         }
         else {
           $expression = $specification['initial_from_field'];
@@ -366,9 +366,9 @@ public function addField($table, $field, $specification, $keys_new = []) {
       }
       elseif (isset($specification['initial_from_field'])) {
         // If we have a initial value, copy it over.
-        if (is_array($specification['initial_from_field'])) {
-          $expression = 'COALESCE(' . $specification['initial_from_field']['field_name'] . ', :default_initial_value)';
-          $arguments = [':default_initial_value' => $specification['initial_from_field']['default_value']];
+        if (isset($specification['initial'])) {
+          $expression = 'COALESCE(' . $specification['initial_from_field'] . ', :default_initial_value)';
+          $arguments = [':default_initial_value' => $specification['initial']];
         }
         else {
           $expression = $specification['initial_from_field'];
diff --git a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
index f94ad4ff2e..9c123417ca 100644
--- a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
+++ b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
@@ -1829,12 +1829,7 @@ protected function getSharedTableFieldSchema(FieldStorageDefinitionInterface $st
         $initial_value = reset($initial_storage_value);
       }
 
-      if ($initial_value_from_field = $storage_definition->getInitialValueFromField()) {
-        $initial_value_field_name = $initial_value_from_field['field_name'];
-        // @todo Implement initial default value support for multi-value fields
-        //   in https://www.drupal.org/node/2883851.
-        $initial_default_value = reset($initial_value_from_field['default_value']);
-
+      if ($initial_value_field_name = $storage_definition->getInitialValueFromField()) {
         // Check that the field used for populating initial values is valid. We
         // must use the last installed version of that, as the new field might
         // be created in an update function and the storage definition of the
@@ -1852,10 +1847,7 @@ protected function getSharedTableFieldSchema(FieldStorageDefinitionInterface $st
           throw new FieldException("Illegal initial value definition on {$storage_definition->getName()}: Both fields have to be stored in the shared entity tables.");
         }
 
-        $initial_value_from_field = [
-          'field_name' => $table_mapping->getColumnNames($initial_value_from_field['field_name']),
-          'default_value' => $initial_default_value,
-        ];
+        $initial_value_from_field = $table_mapping->getColumnNames($initial_value_field_name);
       }
     }
 
@@ -1889,13 +1881,8 @@ protected function getSharedTableFieldSchema(FieldStorageDefinitionInterface $st
       if ($initial_value && isset($initial_value[$field_column_name])) {
         $schema['fields'][$schema_field_name]['initial'] = drupal_schema_get_field_value($column_schema, $initial_value[$field_column_name]);
       }
-      elseif (!empty($initial_value_from_field)) {
-        $schema['fields'][$schema_field_name]['initial_from_field'] = [
-          'field_name' => $initial_value_from_field['field_name'][$field_column_name],
-          'default_value' => $initial_value_from_field['default_value']
-            ? drupal_schema_get_field_value($column_schema, $initial_value_from_field['default_value'][$field_column_name])
-            : NULL,
-        ];
+      if (!empty($initial_value_from_field)) {
+        $schema['fields'][$schema_field_name]['initial_from_field'] = $initial_value_from_field[$field_column_name];
       }
     }
 
diff --git a/core/lib/Drupal/Core/Field/BaseFieldDefinition.php b/core/lib/Drupal/Core/Field/BaseFieldDefinition.php
index f787232a60..8a0cfd3752 100644
--- a/core/lib/Drupal/Core/Field/BaseFieldDefinition.php
+++ b/core/lib/Drupal/Core/Field/BaseFieldDefinition.php
@@ -604,24 +604,8 @@ public function getInitialValueFromField() {
    * @return $this
    */
   public function setInitialValueFromField($field_name, $default_value = NULL) {
-    if ($default_value === NULL) {
-      $default_value = [];
-    }
-    // Unless the default value is an empty array, we may need to transform it.
-    if (!is_array($default_value) || !empty($default_value)) {
-      if (!is_array($default_value)) {
-        $default_value = [[$this->getMainPropertyName() => $default_value]];
-      }
-      elseif (is_array($default_value) && !is_numeric(array_keys($default_value)[0])) {
-        $default_value = [0 => $default_value];
-      }
-    }
-
-    $this->definition['initial_value_from_field'] = [
-      'field_name' => $field_name,
-      'default_value' => $default_value,
-    ];
-
+    $this->definition['initial_value_from_field'] = $field_name;
+    $this->setInitialValue($default_value);
     return $this;
   }
 
diff --git a/core/tests/Drupal/KernelTests/Core/Database/SchemaTest.php b/core/tests/Drupal/KernelTests/Core/Database/SchemaTest.php
index 321f720ab1..82280369b2 100644
--- a/core/tests/Drupal/KernelTests/Core/Database/SchemaTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Database/SchemaTest.php
@@ -530,10 +530,8 @@ public function testSchemaAddField() {
           ['not null' => TRUE, 'initial_from_field' => 'serial_column'],
           [
             'not null' => TRUE,
-            'initial_from_field' => [
-              'field_name' => 'test_nullable_field',
-              'default_value' => 100,
-            ],
+            'initial_from_field' => 'test_nullable_field',
+            'initial'  => 100,
           ],
         ];
 
@@ -660,7 +658,7 @@ protected function assertFieldCharacteristics($table_name, $field_name, $field_s
     }
 
     // Check that the initial value from another field has been registered.
-    if (isset($field_spec['initial_from_field']) && !is_array($field_spec['initial_from_field'])) {
+    if (isset($field_spec['initial_from_field']) && !isset($field_spec['initial'])) {
       // There should be no row with a value different than
       // $field_spec['initial_from_field'].
       $count = db_select($table_name)
@@ -671,7 +669,7 @@ protected function assertFieldCharacteristics($table_name, $field_name, $field_s
         ->fetchField();
       $this->assertEqual($count, 0, 'Initial values from another field filled out.');
     }
-    elseif (isset($field_spec['initial_from_field']) && is_array($field_spec['initial_from_field'])) {
+    elseif (isset($field_spec['initial_from_field']) && isset($field_spec['initial'])) {
       // There should be no row with a value different than '100'.
       $count = db_select($table_name)
         ->fields($table_name, ['serial_column'])