The surge in affection for Kate Bush's Running Up That Hill looks likely to send her to number one this week.
The 80s ballad is already at number two, thanks to its use in the hit Netflix series Stranger Things.
Its chances of making the top have now increased, after the Charts enacted a rule that stops older songs being penalised if their streams surge.
Running Up That Hill is currently the UK's most-streamed song, averaging 700,000 plays per day on Spotify.
In previous weeks, those streams would have counted as 3,500 "sales". This week, that figure will double to 7,000.
That's all because of an esoteric, but important, rule dictating the way the charts are calculated in the streaming era.
The Top 40 used to consist of songs you could buy in a record shop, and every sale was equal. If a record label hadn't pressed enough copies of a 7-inch or CD single, it might miss the chart altogether.
In some instances, record labels even stopped manufacturing a hit single in order to convince people to buy the album instead (Wet Wet Wet's Love Is All Around and the Fugees' Killing Me Softly both suffered this fate).
But in the streaming era, every song is available everywhere all the time. This poses the charts with a problem. If you counted streams on a like-for-like basis, classic songs like The Killers' Mr Brightside would never leave the Top 40; and a modern hit like Ed Sheeran's Bad Habits would currently be spending its 50th week in the Top 10.
In order to give other artists a chance and keep the charts from becoming stale, the record industry invented something called "accelerated decline".
It works like this. A new record earns one "sale" when it is streamed 100 times on a subscription service like Apple Music or Spotify Premium; or 600 times on an ad-funded service. But older songs need to attract 200 premium / 1,200 ad-funded streams before a "sale" is counted.
Which leads to the bizarre situation where Running Up That Hill was comfortably the most-streamed song in the UK last week (with more than 2.5 million plays) but Harry Styles was able to waltz into the number one spot because his song, As It Was, enjoyed a more favourable streams-to-sales ratio.
This week, the playing field has been levelled.
The Chart Supervisory Committee, which oversees the Top 40, revoked the accelerated decline rule for Running Up That Hill over the weekend, meaning its streams are now worth the same as all the singles around it, including Harry Styles.
The situation is unusual, but not entirely without precedent. Under chart rules, the "standard" streaming ratios can be applied to any single if its sales increase by 25% week-on-week.
Record labels can also request a "manual reset" to the ratio "in exceptional circumstances, where a track is being scheduled for promotion".
This is exactly what EMI did for Kate Bush. It's not clear why the request took a fortnight to be enacted (the rules state that one week's notice is sufficient) but it seems no-one could deny the feel-good factor of granting the star her first number one single since 1978's Wuthering Heights.
By Monday, the singer was already 5,000 sales ahead of Styles, a lead that's unlikely to be surpassed.
Her success isn't just limited to the UK. Propelled by Stranger Things, Running Up That Hill has appeared in the top 10 in Australia, the US, France and Germany.
The star has reacted with a mixture of shock and gratitude.
"It's hard to take in the speed at which this has all been happening," she wrote to fans in a message on her website. "So many young people who love the show [are] discovering the song for the first time."
"The response to Running Up That Hill is something that has had its own energy and volition. A direct relationship between the shows and their audience and one that has stood completely outside of the music business. We've all been astounded to watch the track explode!"
The song's popularity could even keep growing. According to Stranger Things creators The Duffer Brothers, Running Up That Hill plays an even bigger role in the second half of the current series, which premieres in July.
One person who already knows how the story ends is Bush herself. She watches every scene her music is featured in, the brothers told Empire magazine, and the track has a "really special spot in the finale".
"She's been nothing but cool," said Ross Duffer. "We keep going back to her, like, 'Can we use the song here? How about here? I hope we're not being annoying!"