Installing module generates database error

Installing this module gave me the following error:

* user warning: All parts of a PRIMARY KEY must be NOT NULL; If you need NULL in a key, use UNIQUE instead query: CREATE TABLE if not exists relatedcontent ( nid int, include_nid int, PRIMARY KEY (nid, include_nid) ) /*!40100 DEFAULT CHARACTER SET utf8 */ in .../drupal/includes/database.mysql.inc on line 172.
* Failed to create database table for RelatedContent.

Adding NOT NULL to each column and running the query manually seemed to fix the problem:

CREATE TABLE if not exists relatedcontent ( nid int NOT NULL, include_nid int NOT NULL, PRIMARY KEY (nid, include_nid) )