I have an existing table created with this migration code:

```
Schema::create('mytable', function (Blueprint $table) {

 $table->increments('id');
 $table->double('mycolumn',8,2)->unsigned()->default(0);
 $table->timestamps();

});

```

Then I have created another migration file to adjust the value range of my `mycolumn` field with the migration file below.

```
Schema::table('mytable', function (Blueprint $table) {

 $table->double('mycolumn',15,2)->unsigned()->default(0)->change();

});

```

However I am getting an error:

```
In DBALException.php line 283:

  Unknown column type "double" requested. Any Doctrine type that you use has to be registered with \Doctrine\DBAL\Types\Type::addType(). You can get a li
  st of all the known types with \Doctrine\DBAL\Types\Type::getTypesMap(). If this error occurs during database introspection then you might have forgott
  en to register all database types for a Doctrine Type. Use AbstractPlatform#registerDoctrineTypeMapping() or have your custom types implement Type#getM
  appedDatabaseTypes(). If the type name is empty you might have a problem with the cache or forgot some mapping information.

```

What am I missing?