diff --git a/core/modules/text/src/Plugin/migrate/cckfield/TextField.php b/core/modules/text/src/Plugin/migrate/cckfield/TextField.php
index 24dd450d85..02a08b999c 100644
--- a/core/modules/text/src/Plugin/migrate/cckfield/TextField.php
+++ b/core/modules/text/src/Plugin/migrate/cckfield/TextField.php
@@ -58,6 +58,18 @@ public function processCckFieldValues(MigrationInterface $migration, $field_name
       }
       $process['value']['map'][$checked_value] = 1;
     }
+    elseif (isset($field_info['instance_settings']['text_processing'])
+      && $field_info['instance_settings']['text_processing'] === 0
+    ) {
+      // This is a D7 plain text field, no formats supported.
+      $process = [
+        'value' => 'value',
+        'format' => [
+          'plugin' => 'default_value',
+          'default_value' => 'plain_text',
+        ],
+      ];
+    }
     else {
       // See \Drupal\migrate_drupal\Plugin\migrate\source\d6\User::baseFields(),
       // signature_format for an example of the YAML that represents this
diff --git a/core/modules/text/tests/src/Unit/Migrate/TextFieldTest.php b/core/modules/text/tests/src/Unit/Migrate/TextFieldTest.php
index d7dfcc679e..013116c5d1 100644
--- a/core/modules/text/tests/src/Unit/Migrate/TextFieldTest.php
+++ b/core/modules/text/tests/src/Unit/Migrate/TextFieldTest.php
@@ -67,6 +67,30 @@ public function testProcessFilteredTextFieldValues() {
     $this->assertSame('format', $lookup['source']);
   }
 
+  /**
+   * @covers ::processCckFieldValues
+   */
+  public function testProcessUnfilteredTextFieldValues() {
+    $field_info = [
+      'widget_type' => 'text_textfield',
+      'instance_settings' => [
+        'text_processing' => 0,
+      ],
+    ];
+    $this->plugin->processCckFieldValues($this->migration, 'field_test', $field_info);
+
+    $process = $this->migration->getProcess();
+    $this->assertSame('iterator', $process['plugin']);
+    $this->assertSame('field_test', $process['source']);
+
+    // Ensure unfiltered D7 text fields are marked as plain text.
+    $this->assertSame('value', $process['process']['value']);
+    $this->assertSame([
+      'plugin' => 'default_value',
+      'default_value' => 'plain_text',
+    ], $process['process']['format']);
+  }
+
   /**
    * @covers ::processCckFieldValues
    */