diff --git a/src/wp-includes/class-wp-customize-setting.php b/src/wp-includes/class-wp-customize-setting.php
index f89797425c..83a5b76d61 100644
--- a/src/wp-includes/class-wp-customize-setting.php
+++ b/src/wp-includes/class-wp-customize-setting.php
@@ -587,7 +587,7 @@ class WP_Customize_Setting {
 		$id_base = $this->id_data['base'];
 		if ( 'option' === $this->type ) {
 			return get_option( $id_base, $default );
-		} else if ( 'theme_mod' ) {
+		} elseif ( 'theme_mod' === $this->type ) {
 			return get_theme_mod( $id_base, $default );
 		} else {
 			/*
@@ -616,7 +616,7 @@ class WP_Customize_Setting {
 				$autoload = self::$aggregated_multidimensionals[ $this->type ][ $this->id_data['base'] ]['autoload'];
 			}
 			return update_option( $id_base, $value, $autoload );
-		} else if ( 'theme_mod' ) {
+		} elseif ( 'theme_mod' === $this->type ) {
 			set_theme_mod( $id_base, $value );
 			return true;
 		} else {
diff --git a/tests/phpunit/tests/customize/setting.php b/tests/phpunit/tests/customize/setting.php
index 86a0743941..9db91a60e8 100644
--- a/tests/phpunit/tests/customize/setting.php
+++ b/tests/phpunit/tests/customize/setting.php
@@ -402,12 +402,21 @@ class Tests_WP_Customize_Setting extends WP_UnitTestCase {
 			'default' => 123,
 			'sanitize_callback' => array( $this->manager->nav_menus, 'intval_base10' ),
 		) );
+
+		/*
+		 * In #36952 the conditions were such that get_theme_mod() be erroneously used
+		 * to source the root value for a custom multidimensional type.
+		 * Add a theme mod with the same name as the custom setting to test fix.
+		 */
+		set_theme_mod( $setting_id, 999 );
 		$this->assertSame( 123, $setting->value() );
+
 		$this->manager->set_post_value( $setting_id, '456' );
 		$setting->preview();
 		$this->assertSame( 456, $setting->value() );
 
 		unset( $this->custom_type_data_previewed, $this->custom_type_data_saved );
+		remove_theme_mod( $setting_id );
 	}
 
 	/**