diff --git a/cores/arduino/WMath.cpp b/cores/arduino/WMath.cpp
index 9fb072f46..247daca69 100644
--- a/cores/arduino/WMath.cpp
+++ b/cores/arduino/WMath.cpp
@@ -49,9 +49,15 @@ long random(long howsmall, long howbig)
   return random(diff) + howsmall;
 }
 
+// well-defined for in_min < in_max, in_min <= x <= in_max,
+// out_min <= out_max
 long map(long x, long in_min, long in_max, long out_min, long out_max)
 {
-  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
+  const long dividend = out_max - out_min;
+  const long divisor = in_max - in_min;
+  const long delta = x - in_min;
+
+  return (delta * dividend + (divisor / 2)) / divisor + out_min;
 }
 
 unsigned int makeWord(unsigned int w) { return w; }