Betting that British voters will opt to leave the European Union on June 23 is now the “risky” trade when it comes to U.K. equities, according to a firm that tracks institutional-investor positioning.

British stocks UKX, +0.73% have traded under a “shroud of uncertainty” ever since the date of the so-called Brexit referendum was announced in February, leading global fund managers to underweight the U.K., according to a Friday note from LuxArbor Institutional Positioning, a Montreal-based data provider that tracks major institutional positioning in financial markets.

Read: ‘Brexit’ isn’t the only thing European investors should worry about

In recent weeks, however, global managers have shifted away from those underweight positions, leaving the U.K. allocation close to market weight, the firm said. The chart below maps out the shift. Managers in the top quartile of performance have steadily increased their U.K. allocation since February, while the past month has seen a “capitulation of the laggers,” with fourth-quartile managers moving from a very-underweight position in February to overweight.

LuxArbor Institutional Positioning

Surveys have been all over the place, lately. The “remain” camp’s lead in a poll of polls maintained by Standard Chartered stands at 7 percentage points, according to Bloomberg , which suggests the outcome is still uncertain. The British pound GBPUSD, -0.1478% ?tumbled to an eight-week low versus the dollar Friday after a poll by the Independent newspaper found growing support for the “leave” camp.

LuxArbor said around 58% of the global funds it tracks are now overweight U.K. stocks, up from 20% a month ago.

Historical data suggests that when managers make such a rapid reduction in underweight positions, they tend to further add to positions in the following days, LuxArbor founder Pierre Lapointe told MarketWatch.

“In other words, if everyone is already overweight by June 23 there might not be [many] buyers left by then. But it’s not the case yet,” he said, via email.

Since managers are still largely market weight, there’s still room for more buying, which is what makes a bet against a “stay” outcome risky.

Moreover, “fund managers might not wait for the actual result before making their move,” he said. “We wouldn't be surprised to see a 5% rally if the ‘remain’ option wins.”