diff --git a/drivers/timers/rtc.c b/drivers/timers/rtc.c
index e375cfa64f..7614000258 100644
--- a/drivers/timers/rtc.c
+++ b/drivers/timers/rtc.c
@@ -819,7 +819,7 @@ static int rtc_unlink(FAR struct inode *inode)
 int rtc_initialize(int minor, FAR struct rtc_lowerhalf_s *lower)
 {
   FAR struct rtc_upperhalf_s *upper;
-  char devpath[16];
+  char devpath[20];
   int ret;
 
   DEBUGASSERT(lower && lower->ops && minor >= 0 && minor < 1000);
@@ -844,11 +844,11 @@ int rtc_initialize(int minor, FAR struct rtc_lowerhalf_s *lower)
   upper->unlinked = false;  /* Driver is not  unlinked */
 #endif
 
-  /* Create the driver name.  There is space for the a minor number up to  6
+  /* Create the driver name.  There is space for the a minor number up to 10
    * characters
    */
 
-  snprintf(devpath, 16, "/dev/rtc%d", minor);
+  snprintf(devpath, sizeof(devpath), "/dev/rtc%d", minor);
 
   /* And, finally, register the new RTC driver */