diff --git a/cpu/cc2538/dev/sys-ctrl.c b/cpu/cc2538/dev/sys-ctrl.c
index df6ba8445..87eabfa44 100644
--- a/cpu/cc2538/dev/sys-ctrl.c
+++ b/cpu/cc2538/dev/sys-ctrl.c
@@ -35,20 +35,39 @@
  * \file
  * Implementation of the cc2538 System Control driver
  */
+#include "contiki.h"
 #include "reg.h"
 #include "cpu.h"
 #include "dev/sys-ctrl.h"
+#include "dev/gpio.h"
+#include "dev/ioc.h"
 
 #include <stdint.h>
+
+#if SYS_CTRL_OSC32K_USE_XTAL
+#define SYS_CTRL_OSCS   0
+#else
+#define SYS_CTRL_OSCS   SYS_CTRL_CLOCK_CTRL_OSC32K
+#endif
 /*---------------------------------------------------------------------------*/
 void
 sys_ctrl_init()
 {
   uint32_t val;
 
+#if SYS_CTRL_OSC32K_USE_XTAL
+  /* Set the XOSC32K_Q pads to analog for crystal */
+  GPIO_SOFTWARE_CONTROL(GPIO_PORT_TO_BASE(GPIO_D_NUM), GPIO_PIN_MASK(6));
+  GPIO_SET_INPUT(GPIO_PORT_TO_BASE(GPIO_D_NUM), GPIO_PIN_MASK(6));
+  ioc_set_over(GPIO_D_NUM, 6, IOC_OVERRIDE_ANA);
+  GPIO_SOFTWARE_CONTROL(GPIO_PORT_TO_BASE(GPIO_D_NUM), GPIO_PIN_MASK(7));
+  GPIO_SET_INPUT(GPIO_PORT_TO_BASE(GPIO_D_NUM), GPIO_PIN_MASK(7));
+  ioc_set_over(GPIO_D_NUM, 7, IOC_OVERRIDE_ANA);
+#endif
+
   /*
    * Desired Clock Ctrl configuration:
-   * 32KHz source: RC
+   * 32KHz source: RC or crystal, according to SYS_CTRL_OSC32K_USE_XTAL
    * System Clock: 32 MHz
    * Power Down Unused
    * I/O Div: 16MHz
@@ -56,11 +75,18 @@ sys_ctrl_init()
    * Rest: Don't care
    */
 
-  val = SYS_CTRL_CLOCK_CTRL_OSC32K | SYS_CTRL_CLOCK_CTRL_OSC_PD
+  val = SYS_CTRL_OSCS | SYS_CTRL_CLOCK_CTRL_OSC_PD
       | SYS_CTRL_CLOCK_CTRL_IO_DIV_16MHZ | SYS_CTRL_CLOCK_CTRL_SYS_DIV_16MHZ;
   REG(SYS_CTRL_CLOCK_CTRL) = val;
 
-  while((REG(SYS_CTRL_CLOCK_STA) & SYS_CTRL_CLOCK_STA_OSC) != 0);
+  while((REG(SYS_CTRL_CLOCK_STA) & (SYS_CTRL_CLOCK_STA_OSC32K |
+        SYS_CTRL_CLOCK_STA_OSC)) != SYS_CTRL_OSCS);
+
+#if SYS_CTRL_OSC32K_USE_XTAL
+  /* Wait for the 32-kHz crystal oscillator to stabilize */
+  while(REG(SYS_CTRL_CLOCK_STA) & SYS_CTRL_CLOCK_STA_SYNC_32K);
+  while(!(REG(SYS_CTRL_CLOCK_STA) & SYS_CTRL_CLOCK_STA_SYNC_32K));
+#endif
 }
 /*---------------------------------------------------------------------------*/
 void
diff --git a/cpu/cc2538/dev/sys-ctrl.h b/cpu/cc2538/dev/sys-ctrl.h
index 8ce6e3193..f63fd5a50 100644
--- a/cpu/cc2538/dev/sys-ctrl.h
+++ b/cpu/cc2538/dev/sys-ctrl.h
@@ -228,11 +228,26 @@
 #define SYS_CTRL_PMCTL_PM0                  0x00000000  /**< PM0 */
 /** @} */
 /*---------------------------------------------------------------------------*/
+/** \name SysCtrl 32-kHz oscillator selection
+ *
+ * Prefer the crystal oscillator for time accuracy, and the RC oscillator for
+ * cost and power consumption
+ * @{
+ */
+/* Defaults to RC oscillator unless the configuration tells us otherwise */
+#ifdef SYS_CTRL_CONF_OSC32K_USE_XTAL
+#define SYS_CTRL_OSC32K_USE_XTAL        SYS_CTRL_CONF_OSC32K_USE_XTAL
+#else
+#define SYS_CTRL_OSC32K_USE_XTAL        0
+#endif
+/** @} */
+/*---------------------------------------------------------------------------*/
 /** \name SysCtrl functions
  * @{
  */
 /** \brief Initialises the System Control Driver. The main purpose of this
- * function is to power up and select clocks and oscillators */
+ * function is to power up and select clocks and oscillators
+ * \note This function depends on ioc_init() having been called beforehand. */
 void sys_ctrl_init();
 
 /** \brief Generates a warm reset through the SYS_CTRL_PWRDBG register */
diff --git a/platform/cc2538dk/contiki-main.c b/platform/cc2538dk/contiki-main.c
index f834368c9..1b76d3bba 100644
--- a/platform/cc2538dk/contiki-main.c
+++ b/platform/cc2538dk/contiki-main.c
@@ -127,12 +127,12 @@ int
 main(void)
 {
   nvic_init();
+  ioc_init();
   sys_ctrl_init();
   clock_init();
   lpm_init();
   rtimer_init();
   gpio_init();
-  ioc_init();
 
   leds_init();
   fade(LEDS_YELLOW);