--- a/asm/Makefile
+++ b/asm/Makefile
@@ -1,7 +1,7 @@
       CC = gcc -g -ggdb
   CFLAGS = -Wall -O2 -Iinclude
  LDFLAGS =
-    NASM = nasm -f elf -Iinclude/
+    NASM = nasm -f elf64 -Iinclude/
   TARGET = stackinfo
 OBJECTS  = main.o
 OBJECTS += get_sp.o