# Assert in box2d (SOLVED) **URL:** \ **Category:** Bugs\ **Created:** [January 17, 2016, 11:13am UTC](https://forum.defold.com/t/assert-in-box2d-solved/792 "2016-01-17T11:13:57Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Jacob](https://forum-defold.b-cdn.net/letter_avatar_proxy/v4/letter/j/f1d935/32.png) [@Jacob](https://forum.defold.com/u/Jacob)\ **Post date:** [January 17, 2016, 11:13am UTC](https://forum.defold.com/t/assert-in-box2d-solved/792/1 "2016-01-17T11:13:58Z")
Every once in a while, I get this assert: Assertion failed: (bd-\>position.IsValid()), function b2Body, file ../src/box2d/Box2D/Dynamics/b2Body.cpp, line 27. Haven’t been able to track it down to a specific event, other than it involves a certain game object containing kinematic collision type. ---
**Author:** ![britzl](https://forum-defold.b-cdn.net/user_avatar/forum.defold.com/britzl/32/23_2.png) [@britzl](https://forum.defold.com/u/britzl)\ **Post date:** [January 17, 2016, 12:51pm UTC](https://forum.defold.com/t/assert-in-box2d-solved/792/2 "2016-01-17T12:51:19Z")
Interesting. It would be great if this could be isolated to a reproducible minimal example, or the steps to reproduce it could be clarified. Could you tell me a bit more about the setup? What kind of game is it? What kind of collision objects do you have? How many? And game objects, are they spawned and destroyed a lot? @sicher: Do you recognise this? Anything else we need to know? ---
**Author:** ![sicher](https://forum-defold.b-cdn.net/user_avatar/forum.defold.com/sicher/32/8_2.png) [@sicher](https://forum.defold.com/u/sicher)\ **Post date:** [January 17, 2016, 4:46pm UTC](https://forum.defold.com/t/assert-in-box2d-solved/792/3 "2016-01-17T16:46:54Z")
Not sure. Something here might ring a bell but that would be for something I saw ages ago. It would be great to get hold of a good isolated repro-case. ---
**Author:** ![Jacob](https://forum-defold.b-cdn.net/letter_avatar_proxy/v4/letter/j/f1d935/32.png) [@Jacob](https://forum.defold.com/u/Jacob)\ **Post date:** [January 18, 2016, 6:16pm UTC](https://forum.defold.com/t/assert-in-box2d-solved/792/4 "2016-01-18T18:16:40Z")
I will try to create an isolated case. ---
**Author:** ![britzl](https://forum-defold.b-cdn.net/user_avatar/forum.defold.com/britzl/32/23_2.png) [@britzl](https://forum.defold.com/u/britzl)\ **Post date:** [January 25, 2016, 2:29pm UTC](https://forum.defold.com/t/assert-in-box2d-solved/792/5 "2016-01-25T14:29:57Z")
Were you able to isolate this or did you find a solution? ---
**Author:** ![Jacob](https://forum-defold.b-cdn.net/letter_avatar_proxy/v4/letter/j/f1d935/32.png) [@Jacob](https://forum.defold.com/u/Jacob)\ **Post date:** [January 25, 2016, 11:21pm UTC](https://forum.defold.com/t/assert-in-box2d-solved/792/6 "2016-01-25T23:21:39Z")
It’s on my to-do list. Will get there eventually. ---
**Author:** ![Ragnar\_Svensson](https://forum-defold.b-cdn.net/letter_avatar_proxy/v4/letter/r/b5ac83/32.png) [@Ragnar\_Svensson](https://forum.defold.com/u/Ragnar_Svensson)\ **Post date:** [January 27, 2016, 4:22pm UTC](https://forum.defold.com/t/assert-in-box2d-solved/792/7 "2016-01-27T16:22:19Z")
The position of the game object you are creating is not numerically valid (a number Box2D does not like to have in its calculations, essentially something that would destroy or destabilise the physics). Did you divide something with 0? Are you spawning that game object? If so, could you try printing the position of it before spawning? This should be handled more gracefully with a clearer error message. ---
**Author:** ![Jacob](https://forum-defold.b-cdn.net/letter_avatar_proxy/v4/letter/j/f1d935/32.png) [@Jacob](https://forum.defold.com/u/Jacob)\ **Post date:** [January 27, 2016, 6:23pm UTC](https://forum.defold.com/t/assert-in-box2d-solved/792/8 "2016-01-27T18:23:48Z")
You’re right, can see from the trace that we are passing nan values to set\_position before an assert. Thanks!