diff --git a/hardware/arduino/avr/cores/arduino/Arduino.h b/hardware/arduino/avr/cores/arduino/Arduino.h
index 9c57d54bd..7bf51193a 100644
--- a/hardware/arduino/avr/cores/arduino/Arduino.h
+++ b/hardware/arduino/avr/cores/arduino/Arduino.h
@@ -32,7 +32,7 @@ void yield(void);
 #define TWO_PI 6.283185307179586476925286766559
 #define DEG_TO_RAD 0.017453292519943295769236907684886
 #define RAD_TO_DEG 57.295779513082320876798154814105
-#define EULER = 2.718281828459045235360287471352
+#define EULER 2.718281828459045235360287471352
 
 #define SERIAL  0x0
 #define DISPLAY 0x1
diff --git a/hardware/arduino/sam/cores/arduino/wiring_constants.h b/hardware/arduino/sam/cores/arduino/wiring_constants.h
index 770d8a3af..a3cd0d00d 100644
--- a/hardware/arduino/sam/cores/arduino/wiring_constants.h
+++ b/hardware/arduino/sam/cores/arduino/wiring_constants.h
@@ -38,7 +38,7 @@ extern "C"{
 #define TWO_PI 6.283185307179586476925286766559
 #define DEG_TO_RAD 0.017453292519943295769236907684886
 #define RAD_TO_DEG 57.295779513082320876798154814105
-#define EULER = 2.718281828459045235360287471352
+#define EULER 2.718281828459045235360287471352
 
 #define SERIAL  0x0
 #define DISPLAY 0x1