diff --git a/src/posix/platform/alarm.cpp b/src/posix/platform/alarm.cpp
index dd5d47e90..fc28af936 100644
--- a/src/posix/platform/alarm.cpp
+++ b/src/posix/platform/alarm.cpp
@@ -159,8 +159,11 @@ exit:
             remaining = 1;
         }
 
-        aTimeout->tv_sec  = (time_t)(remaining / US_PER_S);
-        aTimeout->tv_usec = remaining % US_PER_S;
+        if (remaining < aTimeout->tv_sec * US_PER_S + aTimeout->tv_usec)
+        {
+            aTimeout->tv_sec  = static_cast<time_t>(remaining / US_PER_S);
+            aTimeout->tv_usec = static_cast<suseconds_t>(remaining % US_PER_S);
+        }
     }
 }