A trial run is set to start on Monday in the industrial complex in Gaeseong for South Korean factories, whose operations North Korea shut down in April in protest against military drills. The South Korean companies operating the factories may heave a sigh of relief at long last.

Yet, the companies should be reminded that their operations in the North Korean border town across the heavily armed Demilitarized Zone are still at the mercy of fickle inter-Korean relations, which the North may plunge into animosity anytime.

True, North Korea gave the South assurances that normal operations would not be affected by any security development in the future. Paraphrased, the remark meant that it would not shut down the industrial complex, citing joint South Korean-U.S. military exercises, as it did in April. Indeed, it remained silent when South Korea and the United States conducted a new round of joint military maneuvers in August.

But this change in attitude should not lull the companies into complacency. North Korea did not shut down the complex because it had not previously committed itself to unhindered operations. Such a commitment had already been made when South and North Korea had agreed to build a joint industrial complex in Gaeseong in August 2000, two months after President Kim Dae-jung and his counterpart Kim Jong-il had held the first inter-Korean summit in Pyongyang.

No matter what, inter-Korean economic relations, including operations in the industrial complex, are destined to be affected by security developments on the Korean Peninsula. North Korea will surely suspend operations again if it believes it serves its interests.

When it withdrew workers from the complex, North Korea apparently believed the South would beg to resume operations. On the contrary, President Park Geun-hye’s administration told the North that it would not allow the companies to restart their factories unless it was assured that the industrial complex would not be arbitrarily closed again.

With no such assurance forthcoming, the Park administration started to take steps to withdraw the companies from the complex and compensate them for their losses. At that point, the North took the South seriously and offered to accept the South Korean demands.

As the industrial complex is preparing to resume operations, South and North Korea still have loose ends to tie up. At the top of the list is compensation for the companies, which sustained huge losses. The North offers to waive taxes for the 2013 fiscal year. But that surely will not be enough.

Another issue is North Korea’s demand for the wages that were not paid to the workers during the five-month hiatus. South Korea will have to uphold the “no work, no pay” principle in negotiations, reminding the North that it withdrew the workers of its own accord.