diff --git a/plugins/optimization-detective/class-od-html-tag-processor.php b/plugins/optimization-detective/class-od-html-tag-processor.php
index 1c21ee6bb1..1c2a660087 100644
--- a/plugins/optimization-detective/class-od-html-tag-processor.php
+++ b/plugins/optimization-detective/class-od-html-tag-processor.php
@@ -266,9 +266,6 @@ public function open_tags(): Generator {
 	 * @param string $message Warning message.
 	 */
 	private function warn( string $message ) {
-		if ( ! function_exists( 'wp_trigger_error' ) ) {
-			return;
-		}
 		wp_trigger_error(
 			__CLASS__ . '::open_tags',
 			esc_html( $message )
diff --git a/plugins/optimization-detective/load.php b/plugins/optimization-detective/load.php
index 809d6b2308..70958bf024 100644
--- a/plugins/optimization-detective/load.php
+++ b/plugins/optimization-detective/load.php
@@ -3,7 +3,7 @@
  * Plugin Name: Optimization Detective
  * Plugin URI: https://github.com/WordPress/performance/issues/869
  * Description: Uses real user metrics to improve heuristics WordPress applies on the frontend to improve image loading priority.
- * Requires at least: 6.3
+ * Requires at least: 6.4
  * Requires PHP: 7.0
  * Version: 0.1.0
  * Author: WordPress Performance Team
diff --git a/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php b/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php
index a883187523..dafe02fdfd 100644
--- a/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php
+++ b/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php
@@ -117,18 +117,16 @@ public static function get_post( string $slug ) {
 	 * @return OD_URL_Metric[] URL metrics.
 	 */
 	public static function get_url_metrics_from_post( WP_Post $post ): array {
-		$this_function = __FUNCTION__;
-		$trigger_error = static function ( $error ) use ( $this_function ) {
-			if ( function_exists( 'wp_trigger_error' ) ) {
-				wp_trigger_error( $this_function, esc_html( $error ), E_USER_WARNING );
-			}
+		$this_function   = __FUNCTION__;
+		$trigger_warning = static function ( $message ) use ( $this_function ) {
+			wp_trigger_error( $this_function, esc_html( $message ), E_USER_WARNING );
 		};
 
 		$url_metrics_data = json_decode( $post->post_content, true );
 		if ( json_last_error() ) {
-			$trigger_error(
+			$trigger_warning(
 				sprintf(
-				/* translators: 1: Post type slug, 2: Post ID, 3: JSON error message */
+					/* translators: 1: Post type slug, 2: Post ID, 3: JSON error message */
 					__( 'Contents of %1$s post type (ID: %2$s) not valid JSON: %3$s', 'optimization-detective' ),
 					self::SLUG,
 					$post->ID,
@@ -137,9 +135,9 @@ public static function get_url_metrics_from_post( WP_Post $post ): array {
 			);
 			$url_metrics_data = array();
 		} elseif ( ! is_array( $url_metrics_data ) ) {
-			$trigger_error(
+			$trigger_warning(
 				sprintf(
-				/* translators: %s is post type slug */
+					/* translators: %s is post type slug */
 					__( 'Contents of %s post type was not a JSON array.', 'optimization-detective' ),
 					self::SLUG
 				)
@@ -150,7 +148,7 @@ public static function get_url_metrics_from_post( WP_Post $post ): array {
 		return array_values(
 			array_filter(
 				array_map(
-					static function ( $url_metric_data ) use ( $trigger_error ) {
+					static function ( $url_metric_data ) use ( $trigger_warning ) {
 						if ( ! is_array( $url_metric_data ) ) {
 							return null;
 						}
@@ -158,9 +156,9 @@ static function ( $url_metric_data ) use ( $trigger_error ) {
 						try {
 							return new OD_URL_Metric( $url_metric_data );
 						} catch ( OD_Data_Validation_Exception $e ) {
-							$trigger_error(
+							$trigger_warning(
 								sprintf(
-								/* translators: 1: Post type slug. 2: Exception message. */
+									/* translators: 1: Post type slug. 2: Exception message. */
 									__( 'Unexpected shape to JSON array in post_content of %1$s post type: %2$s', 'optimization-detective' ),
 									OD_URL_Metrics_Post_Type::SLUG,
 									$e->getMessage()