diff --git a/os/various/lwip_bindings/arch/sys_arch.c b/os/various/lwip_bindings/arch/sys_arch.c
index 6107de252..950213ef1 100644
--- a/os/various/lwip_bindings/arch/sys_arch.c
+++ b/os/various/lwip_bindings/arch/sys_arch.c
@@ -99,18 +99,18 @@ void sys_sem_signal_S(sys_sem_t *sem) {
 }
 
 u32_t sys_arch_sem_wait(sys_sem_t *sem, u32_t timeout) {
-  systime_t tmo;
-  u32_t time;
+  systime_t tmo, start, remaining;
 
   osalSysLock();
   tmo = timeout > 0 ? MS2ST((systime_t)timeout) : TIME_INFINITE;
-  time = (u32_t)ST2MS(osalOsGetSystemTimeX());
-  if (chSemWaitTimeoutS(*sem, tmo) != MSG_OK)
-    time = SYS_ARCH_TIMEOUT;
-  else
-    time = (u32_t)ST2MS(osalOsGetSystemTimeX()) - time;
+  start = osalOsGetSystemTimeX();
+  if (chSemWaitTimeoutS(*sem, tmo) != MSG_OK) {
+    osalSysUnlock();
+    return SYS_ARCH_TIMEOUT;
+  }
+  remaining = osalOsGetSystemTimeX() - start;
   osalSysUnlock();
-  return time;
+  return (u32_t)ST2MS(remaining);
 }
 
 int sys_sem_valid(sys_sem_t *sem) {
@@ -171,18 +171,18 @@ err_t sys_mbox_trypost(sys_mbox_t *mbox, void *msg) {
 }
 
 u32_t sys_arch_mbox_fetch(sys_mbox_t *mbox, void **msg, u32_t timeout) {
-  u32_t time;
-  systime_t tmo;
+  systime_t tmo, start, remaining;
 
   osalSysLock();
   tmo = timeout > 0 ? MS2ST((systime_t)timeout) : TIME_INFINITE;
-  time = (u32_t)osalOsGetSystemTimeX();
-  if (chMBFetchS(*mbox, (msg_t *)msg, tmo) != MSG_OK)
-    time = SYS_ARCH_TIMEOUT;
-  else
-    time = (u32_t)ST2MS(osalOsGetSystemTimeX()) - time;
+  start = osalOsGetSystemTimeX();
+  if (chMBFetchS(*mbox, (msg_t *)msg, tmo) != MSG_OK) {
+    osalSysUnlock();
+    return SYS_ARCH_TIMEOUT;
+  }
+  remaining = osalOsGetSystemTimeX() - start;
   osalSysUnlock();
-  return time;
+  return (u32_t)ST2MS(remaining);
 }
 
 u32_t sys_arch_mbox_tryfetch(sys_mbox_t *mbox, void **msg) {
diff --git a/readme.txt b/readme.txt
index d6bc68ecf..de3e3fd12 100644
--- a/readme.txt
+++ b/readme.txt
@@ -72,6 +72,9 @@
 *** Releases and Change Log                                               ***
 *****************************************************************************
 
+*** 16.1.3 ***
+- VAR: Fixed missing time convesion in lwIP arch module (bug #696, again).
+
 *** 16.1.2 ***
 - VAR: Fixed missing time convesion in lwIP arch module (bug #696).
 - HAL: Fixed incorrect handling of TIME_IMMEDIATE in the HAL buffer queues