diff --git a/cpu/cc2538/dev/i2c.c b/cpu/cc2538/dev/i2c.c
index 29ded2967..a4683bdc5 100644
--- a/cpu/cc2538/dev/i2c.c
+++ b/cpu/cc2538/dev/i2c.c
@@ -50,7 +50,7 @@ get_sys_clock(void)
 {
   /* Get the clock status diviser */
   return SYS_CTRL_32MHZ /
-         ((REG(SYS_CTRL_CLOCK_STA) & SYS_CTRL_CLOCK_STA_SYS_DIV) + 1);
+         (1 << (REG(SYS_CTRL_CLOCK_STA) & SYS_CTRL_CLOCK_STA_SYS_DIV));
 }
 /*---------------------------------------------------------------------------*/
 void