Google made major strides in improving security coverage for Android smartphones in 2016, but around half of the Android devices in use haven’t seen a security update in a year, according to key conclusions from Google’s annual Android Security Year In Review report.

As the report details, Google has expanded its process for pushing out major security updates. Through its monthly security update program, Google touted that more than 735 million devices received a platform update last year.

Read: Android Is As Secure As Apple's iOS, Google Security Director Claims

However, the process to bring those updates through to manufacturers still has room for improvement. Android security team member Andrew Ludwig told TechCrunch that around 78 percent of flagship Android devices in North America were on a current security update.

Security update frequency isn’t necessarily as important of a line item as features for general buyers, but they’ve increasingly become tied to manufacturer quality. As the Google security report notes, major brands like Samsung, LG and Huawei regularly push out Android updates quickly to phone users. In addition, first-party phones like the Google Pixel and Android One series were designed, in part, to get security updates out more quickly to users.

Read: Is Your Smartphone Spying On You? Phone Cameras, Microphones At Risk Of Hacking, Expert Says

However, the number of users who aren’t on these flagship models poses a more significant security risk. Major Android smartphone companies have come a long way with security updates since Android’s early days, but the report still reflects the stigma Android has with regular security updates.

For Apple’s part, it reported that, as of February 2017, 79 percent of its devices were on iOS 10. 16 percent of devices were running iOS 9, while 5 percent were running older versions of iOS. While Android’s openness as an operating system played a role in its market share and growth among third-party developers, Google has historically struggled to wrangle the sheer number of devices and manufacturers with Android devices on the market.