diff --git a/src/arch/x86_64/memory/mod.rs b/src/arch/x86_64/memory/mod.rs
index c05ce04..23d6d05 100644
--- a/src/arch/x86_64/memory/mod.rs
+++ b/src/arch/x86_64/memory/mod.rs
@@ -79,6 +79,8 @@ pub trait FrameAllocator {
 
 
 pub fn init(boot_info: &BootInformation) {
+    assert_first_call!("memory::init() can only be called once!");
+
     let memory_map_tag = boot_info.memory_map_tag()
         .expect("multiboot: Memory map tag required");
     let elf_sections_tag = boot_info.elf_sections_tag()
diff --git a/src/lib.rs b/src/lib.rs
index caa5899..389c589 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -7,6 +7,8 @@
 
 #[macro_use]
 extern crate log;
+#[macro_use]
+extern crate once;
 extern crate rlibc;
 extern crate spin;
 extern crate volatile;