diff --git a/cores/arduino/Arduino.h b/cores/arduino/Arduino.h
index 91eeb16bc..432882f16 100644
--- a/cores/arduino/Arduino.h
+++ b/cores/arduino/Arduino.h
@@ -91,7 +91,7 @@ void yield(void);
 
 #define min(a,b) ((a)<(b)?(a):(b))
 #define max(a,b) ((a)>(b)?(a):(b))
-#define abs(x) ((x)>0?(x):-(x))
+#define abs(x) ((x)>=0?(x):-(x))
 #define constrain(amt,low,high) ((amt)<(low)?(low):((amt)>(high)?(high):(amt)))
 #define round(x)     ((x)>=0?(long)((x)+0.5):(long)((x)-0.5))
 #define radians(deg) ((deg)*DEG_TO_RAD)