diff --git a/src/userprog/process.c b/src/userprog/process.c
index 9d4b3fc..b43123d 100644
--- a/src/userprog/process.c
+++ b/src/userprog/process.c
@@ -22,6 +22,10 @@
 #include "threads/synch.h"
 #include "devices/timer.h"
 
+/* Defines the native number of bytes processed by the processor
+   (for the purposes of alignment). */
+#define WORD_SIZE 4
+
 /* Keeps track of the position of pointers to user program arguments
    within a linked list. */
 struct arg_elem
@@ -153,7 +157,7 @@ process_init_stack (char *saveptr, void **esp, char *file_name)
 
     /* Calculate the remaining number of bytes that need to be written
        to the user process stack in order to check for possible overflow. */
-    size_t align_size = ((unsigned int) *esp % 4) * sizeof (uint8_t);
+    size_t align_size = ((unsigned int) *esp % WORD_SIZE) * sizeof (uint8_t);
     size_t argv_data_size = (arg_count + 1) * sizeof (char *);
     size_t argv_size = sizeof (char **);
     size_t argc_size = sizeof (int);