diff --git a/os/kernel/src/chschd.c b/os/kernel/src/chschd.c
index 846833286..3ba8b29e9 100644
--- a/os/kernel/src/chschd.c
+++ b/os/kernel/src/chschd.c
@@ -138,19 +138,18 @@ static void wakeup(void *p) {
  * @retval RDY_TIMEOUT if a timeout occurs.
  */
 msg_t chSchGoSleepTimeoutS(tstate_t newstate, systime_t time) {
-  Thread *tp = currp;
 
   if (TIME_INFINITE != time) {
     VirtualTimer vt;
 
-    chVTSetI(&vt, time, wakeup, tp);
+    chVTSetI(&vt, time, wakeup, currp);
     chSchGoSleepS(newstate);
     if (chVTIsArmedI(&vt))
       chVTResetI(&vt);
   }
   else
     chSchGoSleepS(newstate);
-  return tp->p_rdymsg;
+  return currp->p_rdymsg;
 }
 
 /**
diff --git a/os/ports/GCC/ARMCM3/chcore.h b/os/ports/GCC/ARMCM3/chcore.h
index 7d33251ad..7e68d1aae 100644
--- a/os/ports/GCC/ARMCM3/chcore.h
+++ b/os/ports/GCC/ARMCM3/chcore.h
@@ -306,13 +306,13 @@ struct context {
   if (sp - sizeof(struct intctx) - sizeof(Thread) < (char *)_otp)       \
     asm volatile ("movs    r0, #0                               \n\t"   \
                   "b       chDbgPanic");                                \
-  asm volatile ("svc     #0" : : "r" (_otp), "r" (_ntp));               \
+    asm volatile ("svc     #0" : : "r" (_otp), "r" (_ntp) : "memory");  \
 }
 #else /* !CH_DBG_ENABLE_STACK_CHECK */
 #define port_switch(otp, ntp) {                                         \
   register Thread *_otp asm ("r0") = (otp);                             \
   register Thread *_ntp asm ("r1") = (ntp);                             \
-  asm volatile ("svc     #0" : : "r" (_otp), "r" (_ntp));               \
+  asm volatile ("svc     #0" : : "r" (_otp), "r" (_ntp) : "memory");    \
 }
 #endif /* !CH_DBG_ENABLE_STACK_CHECK */