diff --git a/wp-includes/class-wp-theme-json.php b/wp-includes/class-wp-theme-json.php
index d754da957a..7ab626ce8f 100644
--- a/wp-includes/class-wp-theme-json.php
+++ b/wp-includes/class-wp-theme-json.php
@@ -1388,6 +1388,7 @@ class WP_Theme_JSON {
 	 *
 	 * @since 6.1.0
 	 * @since 6.3.0 Reduced specificity for layout margin rules.
+	 * @since 6.5.1 Only output rules referencing content and wide sizes when values exist.
 	 *
 	 * @param array $block_metadata Metadata about the block to get styles for.
 	 * @return string Layout styles for the block.
@@ -1548,6 +1549,16 @@ class WP_Theme_JSON {
 							! empty( $base_style_rule['rules'] )
 						) {
 							foreach ( $base_style_rule['rules'] as $css_property => $css_value ) {
+								// Skip rules that reference content size or wide size if they are not defined in the theme.json.
+								if (
+									is_string( $css_value ) &&
+									( str_contains( $css_value, '--global--content-size' ) || str_contains( $css_value, '--global--wide-size' ) ) &&
+									! isset( $this->theme_json['settings']['layout']['contentSize'] ) &&
+									! isset( $this->theme_json['settings']['layout']['wideSize'] )
+								) {
+									continue;
+								}
+
 								if ( static::is_safe_css_declaration( $css_property, $css_value ) ) {
 									$declarations[] = array(
 										'name'  => $css_property,
diff --git a/wp-includes/version.php b/wp-includes/version.php
index a8a80ca2f9..d531da6969 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.6-alpha-57946';
+$wp_version = '6.6-alpha-57948';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.