What I'm trying to do is to override one single method in Model/Observer.php of other module. I followed this tutorial: http://www.atwix.com/magento/overriding-observers/.

As a result I've created my own module. Its etc\config.xml:

<?xml version="1.0"?>

My observer class itself extends initial observer class (and also my module depends on initial module):

class Package_MyModule_Model_Observer extends Package_TheirModule_Model_Observer
    public function someObserverMethod($observer)

Initial module has several events, that are handled by that observer class (let's say, 10).

When I try to run my code I get the following error: "Mage registry key "_singleton/mymodule/observer" already exists". I've tried all solutions for this error from magento.stackexchange.com and none of them worked for me.

But, and that is interesting, when I add all other missed events to my config.xml (9 of those, that I do not want to override), everything works fine. But I do not want to do that, cause I lose advantages of overriding then.

So my question is: how to override only one method of observer of other module and not get this strange error?

  • Try using the full class name in your config.xml <class>Package_MyModule_Model_Observer</class> see: stackoverflow.com/questions/19142720/…
    – B00MER
    Commented Oct 21, 2015 at 15:55
  • @B00MER, though it didn't help, I'd changed the name for consistency, thanks!
    – Gino Pane
    Commented Oct 22, 2015 at 8:12

1 Answer 1


I don't think the rewrite is required any more since you're already disabling their observer.

Do make sure to add their module as a dependency to your module


                <Package_TheirModule />
  • Dependency was added previously, so it was not the reason. But removing of rewrite actually helped! Thanks a lot! It's strange, cause I'm sure that I have tried to remove that section and haven't seen the difference. Maybe I just missed that:)
    – Gino Pane
    Commented Oct 22, 2015 at 8:15

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