diff --git a/src/emulator.h b/src/emulator.h
index 5a78365..facbfd7 100644
--- a/src/emulator.h
+++ b/src/emulator.h
@@ -9,6 +9,7 @@
 
 #define BYTE_BITS 8
 #define WORD_BITS (BYTE_BITS * sizeof(word))
+#define DWORD_BITS (BYTE_BITS * sizeof(dword))
 
 /************************************
  * STRUCTS