change .nasm extension to .s
diff --git a/build/exe.mk b/build/exe.mk
index 7e4258b..834535f 100644
--- a/build/exe.mk
+++ b/build/exe.mk
@@ -29,7 +29,7 @@
 %.i : %.c
 	$(CC) $(CFLAGS) -E $< -o $@
 
-%.o : %.nasm
+%.o : %.s
 	$(NASM) -f elf -d ELF -i i386/ $< -o $@
 
 .PHONY : clean