EXC_BAD_ACCESS SKPhysicsWorld

I'm really confused on why I am getting an EXC_BAD_ACCESS (code=1, address=0x1c) at [world addJoint:pinJoin];.

JointTest.m

#import "JointTest.h"

@implementation JointTest
-(SKNode *)initWithWorld:(SKPhysicsWorld *)pWorld{
    if(self = [super init]){
       world = pWorld;
       [self attachBodies];
    }
    return self;
}
-(void)attachBodies{
    SKSpriteNode * spriteA = [[SKSpriteNode alloc]initWithImageNamed:@"rocket"];
    SKSpriteNode * spriteB = [[SKSpriteNode alloc]initWithImageNamed:@"rocket"];

    SKPhysicsBody * bodyA = [SKPhysicsBody bodyWithRectangleOfSize:spriteA.size];
    SKPhysicsBody * bodyB = [SKPhysicsBody bodyWithRectangleOfSize:spriteB.size];

    spriteA.position = CGPointMake(150, 300);
    spriteB.position = CGPointMake(150, 300 + spriteB.size.height/2);

    [self addChild:spriteA];
    [self addChild:spriteB];

    bodyA.dynamic = NO;

    spriteA.physicsBody = bodyA;
    spriteB.physicsBody = bodyB;

    SKPhysicsJointPin * pinJoin = [SKPhysicsJointPin jointWithBodyA:spriteA.physicsBody bodyB:spriteB.physicsBody anchor:spriteA.position];
    [world addJoint:pinJoin];

}
@end

JointTest.h

#import <SpriteKit/SpriteKit.h>

@interface JointTest : SKNode{
    SKPhysicsWorld * world;
}
-(SKNode *)initWithWorld:(SKPhysicsWorld *)pWorld;
@end

In the SKScene

JointTest * test = [[JointTest alloc]initWithWorld:self.physicsWorld];
[self addChild:test];

What confuses me is moving the code in the attachBodies method into the scene and calling the the addJoint method with the scene's physicsWorld works great. For instance:

SKSpriteNode * spriteA = [[SKSpriteNode alloc]initWithImageNamed:@"rocket"];
SKSpriteNode * spriteB = [[SKSpriteNode alloc]initWithImageNamed:@"rocket"];

SKPhysicsBody * bodyA = [SKPhysicsBody bodyWithRectangleOfSize:spriteA.size];
SKPhysicsBody * bodyB = [SKPhysicsBody bodyWithRectangleOfSize:spriteB.size];

spriteA.position = CGPointMake(150, 300);
spriteB.position = CGPointMake(150, 300 + spriteB.size.height/2);

[self addChild:spriteA];
[self addChild:spriteB];

bodyA.dynamic = NO;

spriteA.physicsBody = bodyA;
spriteB.physicsBody = bodyB;

SKPhysicsJointPin * pinJoin = [SKPhysicsJointPin jointWithBodyA:spriteA.physicsBody bodyB:spriteB.physicsBody anchor:spriteA.position];
[self.physicsWorld addJoint:pinJoin];

I've been pulling my hair out for a few hours over this so if anyone has an idea I would greatly appreciate it. Thanks!