diff --git a/wp-admin/includes/file.php b/wp-admin/includes/file.php
index b9557b1390..69cbf9c22a 100644
--- a/wp-admin/includes/file.php
+++ b/wp-admin/includes/file.php
@@ -528,10 +528,18 @@ function unzip_file($file, $to) {
 		}
 	}
 
-	if ( class_exists('ZipArchive') && apply_filters('unzip_file_use_ziparchive', true ) )
-		return _unzip_file_ziparchive($file, $to, $needed_dirs);
-	else
-		return _unzip_file_pclzip($file, $to, $needed_dirs);
+	if ( class_exists('ZipArchive') && apply_filters('unzip_file_use_ziparchive', true ) ) {
+		$result = _unzip_file_ziparchive($file, $to, $needed_dirs);
+		if ( true === $result ) {
+			return $result;
+		} elseif ( is_wp_error($result) ) {
+			if ( 'incompatible_archive' != $result->get_error_code() )
+				return $result;
+		}
+		echo "fall through to pcl";
+	}
+	// Fall through to PclZip if ZipArchive is not available, or encountered an error opening the file.
+	return _unzip_file_pclzip($file, $to, $needed_dirs);
 }
 
 /**
@@ -591,6 +599,8 @@ function _unzip_file_ziparchive($file, $to, $needed_dirs = array() ) {
 			return new WP_Error('copy_failed', __('Could not copy file.'), $to . $file['filename']);
 	}
 
+	$z->close();
+
 	return true;
 }