diff --git a/src/wp-includes/global-styles-and-settings.php b/src/wp-includes/global-styles-and-settings.php
index c625166524b63..a0b91a4d219ed 100644
--- a/src/wp-includes/global-styles-and-settings.php
+++ b/src/wp-includes/global-styles-and-settings.php
@@ -264,6 +264,26 @@ function ( $item ) {
  * @return bool Returns true if theme or its parent has a theme.json file, false otherwise.
  */
 function wp_theme_has_theme_json() {
+	static $theme_has_support = null;
+
+	if (
+		null !== $theme_has_support &&
+		/*
+		 * Ignore static cache when `WP_DEBUG` is enabled. Why? To avoid interfering with
+		 * the theme developer's workflow.
+		 *
+		 * @todo Replace `WP_DEBUG` once an "in development mode" check is available in Core.
+		 */
+		! WP_DEBUG &&
+		/*
+		 * Ignore cache when automated test suites are running. Why? To ensure
+		 * the static cache is reset between each test.
+		 */
+		! ( defined( 'WP_RUN_CORE_TESTS' ) && WP_RUN_CORE_TESTS )
+	) {
+		return $theme_has_support;
+	}
+
 	// Does the theme have its own theme.json?
 	$theme_has_support = is_readable( get_stylesheet_directory() . '/theme.json' );