diff --git a/os/ports/GCC/ARMCM3/chcore.c b/os/ports/GCC/ARMCM3/chcore.c
index ad50bfc31..c0a45ffb8 100644
--- a/os/ports/GCC/ARMCM3/chcore.c
+++ b/os/ports/GCC/ARMCM3/chcore.c
@@ -151,8 +151,8 @@ void PendSVVector(void) {
   Thread *otp;
   register struct intctx *sp_thd asm("r12");
 
-  chSysLockFromIsr();
   asm volatile ("push    {lr}");
+  chSysLockFromIsr();
   if (!chSchRescRequiredI()) {
     chSysUnlockFromIsr();
     asm volatile ("pop     {pc}");
diff --git a/os/ports/GCC/ARMCM3/chcore.h b/os/ports/GCC/ARMCM3/chcore.h
index 4b1a5355f..7d33251ad 100644
--- a/os/ports/GCC/ARMCM3/chcore.h
+++ b/os/ports/GCC/ARMCM3/chcore.h
@@ -233,7 +233,7 @@ struct context {
 }
 #else
 #define port_lock() {                                                   \
-  asm volatile ("bl     _port_lock" : : : "r3", "lr");                  \
+  asm volatile ("bl      _port_lock" : : : "r3", "lr");                 \
 }
 #endif
 
@@ -247,7 +247,7 @@ struct context {
 }
 #else
 #define port_unlock() {                                                 \
-  asm volatile ("bl     _port_unlock" : : : "r3", "lr");                \
+  asm volatile ("bl      _port_unlock" : : : "r3", "lr");               \
 }
 #endif