If it ever feels like your older model iPhone gets slower when a new version is released, you aren't wrong.
Apple has admitted to deliberately slowing down the operation of older phones to stop them from shutting down unexpected as the battery ages.
Research carried out by Canadian tech company Primate Labs found iPhones exhibited a greater-than-expected drop in general functioning after the update from iOS 10.2.1 to iOS 11.1.2 in June 2017.
Primate Labs founder John Poole says while updates can accelerate a decrease in performance, the drop is far more pronounced in iPhones.
"The difference between 10.2.0 and 10.2.1 is too abrupt to be just a function of battery condition," he told Geekbench.
"I believe, as do others, that Apple introduced a change to limit performance when battery condition decreases past a certain point."
When your battery deteriorates, performance does too as the flow between the battery and processor is restricted.
Mr Poole says limiting an iPhone's performance hides the fact the phone's battery is aging, which encourages users to replace the entire phone, rather than just the battery.
Apple said in a statement that it does slow old devices down in order to prolong their life.
"Lithium-ion batteries become less capable of supplying peak current demands when in cold conditions, have a low battery charge or as they age over time, which can result in the device unexpectedly shutting down to protect its electronic components."