diff --git a/src/wp-includes/blocks/template-part.php b/src/wp-includes/blocks/template-part.php
index 107f20dbd35b5..838210480ca28 100644
--- a/src/wp-includes/blocks/template-part.php
+++ b/src/wp-includes/blocks/template-part.php
@@ -189,6 +189,10 @@ function build_template_part_block_area_variations() {
  * @return array Array containing the block variation objects.
  */
 function build_template_part_block_instance_variations() {
+	// Block themes are unavailable during installation.
+	if ( wp_installing() ) {
+		return array();
+	}
 	$variations     = array();
 	$template_parts = get_block_templates(
 		array(