diff --git a/src/assembler.h b/src/assembler.h
index 29f1ea9..2d14f06 100644
--- a/src/assembler.h
+++ b/src/assembler.h
@@ -70,7 +70,8 @@
   static const double zero;
   static const double uint8_max_value;
   static const double negative_infinity;
-  static const double nan;
+  static const double canonical_non_hole_nan;
+  static const double the_hole_nan;
 };
 
 
@@ -90,14 +91,18 @@
     Unuse();
     UnuseNear();
   }
-  INLINE(~Label())                { ASSERT(!is_linked()); }
 
-  INLINE(void Unuse())            { pos_ = 0; }
-  INLINE(void UnuseNear())        { near_link_pos_ = 0; }
+  INLINE(~Label()) {
+    ASSERT(!is_linked());
+    ASSERT(!is_near_linked());
+  }
 
-  INLINE(bool is_bound() const)  { return pos_ <  0; }
-  INLINE(bool is_unused() const)  { return pos_ == 0 && near_link_pos_ == 0; }
-  INLINE(bool is_linked() const)  { return pos_ >  0; }
+  INLINE(void Unuse()) { pos_ = 0; }
+  INLINE(void UnuseNear()) { near_link_pos_ = 0; }
+
+  INLINE(bool is_bound() const) { return pos_ <  0; }
+  INLINE(bool is_unused() const) { return pos_ == 0 && near_link_pos_ == 0; }
+  INLINE(bool is_linked() const) { return pos_ >  0; }
   INLINE(bool is_near_linked() const) { return near_link_pos_ > 0; }
 
   // Returns the position of bound or linked labels. Cannot be used
@@ -625,7 +630,8 @@
   static ExternalReference address_of_zero();
   static ExternalReference address_of_uint8_max_value();
   static ExternalReference address_of_negative_infinity();
-  static ExternalReference address_of_nan();
+  static ExternalReference address_of_canonical_non_hole_nan();
+  static ExternalReference address_of_the_hole_nan();
 
   static ExternalReference math_sin_double_function(Isolate* isolate);
   static ExternalReference math_cos_double_function(Isolate* isolate);