diff --git a/src/wp-includes/ms-blogs.php b/src/wp-includes/ms-blogs.php
index f8323dd3b7211..a3c9b89e5daa7 100644
--- a/src/wp-includes/ms-blogs.php
+++ b/src/wp-includes/ms-blogs.php
@@ -209,7 +209,6 @@ function get_blog_details( $fields = null, $get_all = true ) {
 		$details = wp_cache_get( $blog_id . 'short', 'blog-details' );
 	} else {
 		$details = wp_cache_get( $blog_id, 'blog-details' );
-		// If short was requested and full cache is set, we can return.
 		if ( $details ) {
 			if ( ! is_object( $details ) ) {
 				if ( -1 === $details ) {
@@ -220,7 +219,9 @@ function get_blog_details( $fields = null, $get_all = true ) {
 					unset( $details );
 				}
 			} else {
-				return $details;
+				// Full cache is set but short was requested. Discard so a clean
+				// short result is built from WP_Site::get_instance() below.
+				unset( $details );
 			}
 		}
 	}
diff --git a/tests/phpunit/tests/multisite/getBlogDetails.php b/tests/phpunit/tests/multisite/getBlogDetails.php
index 5a374d43dc69a..5feb66347ff8b 100644
--- a/tests/phpunit/tests/multisite/getBlogDetails.php
+++ b/tests/phpunit/tests/multisite/getBlogDetails.php
@@ -193,6 +193,48 @@ public function test_get_blog_details_iterate_over_result( $get_all ) {
 		$this->assertSameSets( $this->get_fields( $get_all ), $result );
 	}
 
+	/**
+	 * @ticket 63518
+	 */
+	public function test_get_blog_details_get_all_true_then_false_returns_short() {
+		$site_id = self::$site_ids['wordpress.org/'];
+
+		// Ensure a clean cache state.
+		wp_cache_delete( $site_id, 'blog-details' );
+		wp_cache_delete( $site_id . 'short', 'blog-details' );
+
+		// Populate the full cache first.
+		$full = get_blog_details( $site_id, true );
+		$this->assertSameSets( $this->get_fields( true ), array_keys( get_object_vars( $full ) ) );
+
+		// A subsequent short request must not return the full result.
+		$short = get_blog_details( $site_id, false );
+		$this->assertSameSets( $this->get_fields( false ), array_keys( get_object_vars( $short ) ) );
+	}
+
+	/**
+	 * @ticket 63518
+	 */
+	public function test_get_blog_details_false_true_false_returns_correct_fields() {
+		$site_id = self::$site_ids['wordpress.org/'];
+
+		// Ensure a clean cache state.
+		wp_cache_delete( $site_id, 'blog-details' );
+		wp_cache_delete( $site_id . 'short', 'blog-details' );
+
+		// Short first.
+		$short1 = get_blog_details( $site_id, false );
+		$this->assertSameSets( $this->get_fields( false ), array_keys( get_object_vars( $short1 ) ) );
+
+		// Full second.
+		$full = get_blog_details( $site_id, true );
+		$this->assertSameSets( $this->get_fields( true ), array_keys( get_object_vars( $full ) ) );
+
+		// Short again — must still return short fields.
+		$short2 = get_blog_details( $site_id, false );
+		$this->assertSameSets( $this->get_fields( false ), array_keys( get_object_vars( $short2 ) ) );
+	}
+
 	public function data_get_all() {
 		return array(
 			array( false ),