diff --git a/cubesatsim/cubesatsim.h b/cubesatsim/cubesatsim.h
index 763b3825..28927dd5 100644
--- a/cubesatsim/cubesatsim.h
+++ b/cubesatsim/cubesatsim.h
@@ -82,7 +82,7 @@
 #define TRUE 1
 #define FALSE 0
 
-#define A 1
+#define A_ 1
 #define B 2
 #define C 3
 #define D 4