diff --git a/includes/class-amp-theme-support.php b/includes/class-amp-theme-support.php
index ac35769410f..38dfd0e053f 100644
--- a/includes/class-amp-theme-support.php
+++ b/includes/class-amp-theme-support.php
@@ -715,7 +715,27 @@ public static function get_template_availability( $query = null ) {
 			if ( ! $has_children ) {
 				$supportable_template = $supportable_templates[ $id ];
 				while ( ! empty( $supportable_template['parent'] ) ) {
-					$parent               = $supportable_template['parent'];
+					$parent = $supportable_template['parent'];
+
+					/*
+					 * If the parent is not amongst the supportable templates, then something is off in terms of hierarchy.
+					 * Either the matching is off-track, or the template is badly configured.
+					 */
+					if ( ! array_key_exists( $parent, $supportable_templates ) ) {
+						_doing_it_wrong(
+							__METHOD__,
+							esc_html(
+								sprintf(
+									/* translators: %s: amp_supportable_templates */
+									__( 'An expected parent was not found. Did you filter %s to not honor the template hierarchy?', 'amp' ),
+									'amp_supportable_templates'
+								)
+							),
+							'1.4'
+						);
+						break;
+					}
+
 					$supportable_template = $supportable_templates[ $parent ];
 
 					// Let the child supported status override the parent's supported status.
@@ -922,8 +942,8 @@ public static function get_supportable_templates() {
 		}
 
 		$taxonomy_args = [
-			'_builtin'           => false,
-			'publicly_queryable' => true,
+			'_builtin' => false,
+			'public'   => true,
 		];
 		foreach ( get_taxonomies( $taxonomy_args, 'objects' ) as $taxonomy ) {
 			$templates[ sprintf( 'is_tax[%s]', $taxonomy->name ) ] = [
@@ -936,8 +956,8 @@ public static function get_supportable_templates() {
 		}
 
 		$post_type_args = [
-			'has_archive'        => true,
-			'publicly_queryable' => true,
+			'has_archive' => true,
+			'public'      => true,
 		];
 		foreach ( get_post_types( $post_type_args, 'objects' ) as $post_type ) {
 			$templates[ sprintf( 'is_post_type_archive[%s]', $post_type->name ) ] = [
diff --git a/tests/php/test-class-amp-theme-support.php b/tests/php/test-class-amp-theme-support.php
index 16cf8d35f7c..49143d9b4ef 100644
--- a/tests/php/test-class-amp-theme-support.php
+++ b/tests/php/test-class-amp-theme-support.php
@@ -783,8 +783,8 @@ public function test_get_template_availability_with_ambiguity() {
 		register_post_type(
 			$custom_post_type,
 			[
-				'has_archive'        => true,
-				'publicly_queryable' => true,
+				'has_archive' => true,
+				'public'      => true,
 			]
 		);
 		self::factory()->post->create(
@@ -813,6 +813,43 @@ public function test_get_template_availability_with_ambiguity() {
 		$this->assertEquals( 'is_search', $availability['template'] );
 	}
 
+	/**
+	 * Test get_template_availability with broken parent relationship.
+	 *
+	 * @covers AMP_Theme_Support::get_template_availability()
+	 */
+	public function test_get_template_availability_with_missing_parent() {
+		AMP_Options_Manager::update_option( 'supported_templates', [ 'missing_parent' ] );
+		add_theme_support( AMP_Theme_Support::SLUG );
+		add_filter(
+			'amp_supportable_templates',
+			static function ( $templates ) {
+				$templates['missing_parent'] = [
+					'label'    => 'Missing parent',
+					'parent'   => 'is_unknown',
+					'callback' => static function( WP_Query $query ) {
+						return false !== $query->get( 'missing_parent', false );
+					},
+				];
+				return $templates;
+			}
+		);
+		add_filter(
+			'query_vars',
+			static function ( $vars ) {
+				$vars[] = 'missing_parent';
+				return $vars;
+			}
+		);
+
+		// Test missing_parent.
+		$this->go_to( '/?missing_parent=1' );
+		$this->setExpectedIncorrectUsage( 'AMP_Theme_Support::get_template_availability' );
+		$availability = AMP_Theme_Support::get_template_availability();
+		$this->assertTrue( $availability['supported'] );
+		$this->assertEquals( 'missing_parent', $availability['template'] );
+	}
+
 	/**
 	 * Test get_supportable_templates.
 	 *