diff --git a/src/wp-includes/class-wp-query.php b/src/wp-includes/class-wp-query.php
index 3fcb942aa7..e79f460fc5 100644
--- a/src/wp-includes/class-wp-query.php
+++ b/src/wp-includes/class-wp-query.php
@@ -2020,8 +2020,7 @@ class WP_Query {
 		}
 
 		if ( isset( $q['page'] ) ) {
-			$q['page'] = trim( $q['page'], '/' );
-			$q['page'] = absint( $q['page'] );
+			$q['page'] = is_scalar( $q['page'] ) ? absint( trim( $q['page'], '/' ) ) : 0;
 		}
 
 		// If true, forcibly turns off SQL_CALC_FOUND_ROWS even when limits are present.
diff --git a/tests/phpunit/tests/query/invalidQueries.php b/tests/phpunit/tests/query/invalidQueries.php
index 4c0b631f80..0cec942245 100644
--- a/tests/phpunit/tests/query/invalidQueries.php
+++ b/tests/phpunit/tests/query/invalidQueries.php
@@ -159,4 +159,20 @@ class Tests_Query_InvalidQueries extends WP_UnitTestCase {
 		// Only the published post should be returned.
 		$this->assertCount( 1, $query->posts );
 	}
+
+	/**
+	 * Ensure a non-scalar page parameter does not throw a fatal error for trim().
+	 *
+	 * @ticket 56558
+	 * @covers WP_Query::get_posts
+	 */
+	public function test_non_scalar_page_value() {
+		$query = new WP_Query(
+			array(
+				'page' => array( 1, 2, 3 ),
+			)
+		);
+
+		$this->assertSame( 0, $query->query_vars['page'] );
+	}
 }