diff --git a/include/mes/lib-mini.h b/include/mes/lib-mini.h
index 28acb926..48d91362 100644
--- a/include/mes/lib-mini.h
+++ b/include/mes/lib-mini.h
@@ -41,11 +41,7 @@
    for that by multiplying with M2_PTR_SIZE when using (char)
    pointers. */
 #if __M2__
-#if __x86_64__
-#define M2_PTR_SIZE 8
-#else
-#define M2_PTR_SIZE 4
-#endif
+#define M2_PTR_SIZE sizeof (void*)
 #else
 #define M2_PTR_SIZE 1
 #endif
diff --git a/include/mes/mes.h b/include/mes/mes.h
index 3f5e64b5..c189ab69 100644
--- a/include/mes/mes.h
+++ b/include/mes/mes.h
@@ -57,11 +57,7 @@ struct scm
    for that by multiplying with M2_CELL_SIZE when using cell
    pointers. */
 #if __M2__
-#if __x86_64__
-#define M2_CELL_SIZE 24
-#else
-#define M2_CELL_SIZE 12
-#endif
+#define M2_CELL_SIZE sizeof (struct scm)
 #else
 #define M2_CELL_SIZE 1
 #endif