diff --git a/src/cpu/types.hpp b/src/cpu/types.hpp
index 52f361f..4f0ebc6 100644
--- a/src/cpu/types.hpp
+++ b/src/cpu/types.hpp
@@ -18,6 +18,13 @@ typedef union {
     Int signed_int;
 } SignedInt;
 
+typedef union {
+    struct {
+        Long value : 63;
+        Int signal : 1;
+    } long_with_msb;
+} SignedLong;
+
 //IEEE floating point alias
 typedef float Float;
 typedef double Double;