diff --git a/library/init/lean/ir/extract_cpp.lean b/library/init/lean/ir/extract_cpp.lean
index 691d7c9b7b..7a195f8038 100644
--- a/library/init/lean/ir/extract_cpp.lean
+++ b/library/init/lean/ir/extract_cpp.lean
@@ -152,19 +152,28 @@ match op with
 | binop.eq   := emit_arith t x y z "==" "lean::big_eq"
 | binop.ne   := emit_arith t x y z "!=" "lean::big_nq"
 
+
+/-- Emit `x := op(y)` -/
+def emit_x_op_y (x : var) (op : string) (y : var) : extract_m unit :=
+emit_var x >> emit " := " >> emit op >> emit "(" >> emit_var y >> emit ")"
+
 def emit_unop (x : var) (t : type) (op : unop) (y : var) : extract_m unit :=
 match op with
-| unop.not          := return () -- TODO
-| unop.neg          := return () -- TODO
-| unop.scalar       := return () -- TODO
-| unop.shared       := return () -- TODO
-| unop.copy_array   := return () -- TODO
-| unop.copy_sarray  := return () -- TODO
-| unop.box          := return () -- TODO
-| unop.unbox        := return () -- TODO
-| unop.unbox_bignum := return () -- TODO
-| unop.box_bignum   := return () -- TODO
-| unop.cast         := return () -- TODO
+| unop.not          :=
+  (match t with
+   | type.bool      := emit_x_op_y x "!" y
+   | _              := emit_x_op_y x "~" y)
+| unop.neg          :=
+  (match t with
+   | type.object    := emit_x_op_y x "lean::big_neg" y
+   | _              := emit_x_op_y x "-" y)
+| unop.scalar       := emit_x_op_y x "lean::is_scalar" y
+| unop.shared       := emit_x_op_y x "lean::is_shared" y
+| unop.copy_array   := emit_x_op_y x "lean::copy_array" y
+| unop.copy_sarray  := emit_x_op_y x "lean::copy_sarray" y
+| unop.box          := emit_x_op_y x "lean::box" y
+| unop.unbox        := emit_x_op_y x "lean::unbox" y
+| unop.cast         := emit_var x >> emit " := static_cast<" >> emit_type t >> emit ">(" >> emit_var y >> emit ")"
 
 def emit_lit (x : var) (t : type) (l : literal) : extract_m unit :=
 return () -- TODO
diff --git a/library/init/lean/ir/format.lean b/library/init/lean/ir/format.lean
index ca7471daea..0179db28f3 100644
--- a/library/init/lean/ir/format.lean
+++ b/library/init/lean/ir/format.lean
@@ -51,7 +51,6 @@ def unop.to_format : unop → format
 | unop.not         := "not"        | unop.neg          := "neg"
 | unop.scalar      := "scalar"     | unop.shared       := "shared"
 | unop.box         := "box"        | unop.unbox        := "unbox"
-| unop.box_bignum  := "box_bignum" | unop.unbox_bignum := "unbox_bignum"
 | unop.cast        := "cast"
 | unop.copy_array  := "copy_array" | unop.copy_sarray  := "copy_sarray"
 
diff --git a/library/init/lean/ir/ir.lean b/library/init/lean/ir/ir.lean
index 7f1b312be9..3fba59b078 100644
--- a/library/init/lean/ir/ir.lean
+++ b/library/init/lean/ir/ir.lean
@@ -47,7 +47,7 @@ instance type_has_dec_eq : decidable_eq type :=
 /- END of TEMPORARY HACK for (decidable_eq type) -/
 
 inductive unop
-| not | neg | scalar | shared | cast | box | unbox | box_bignum | unbox_bignum
+| not | neg | scalar | shared | cast | box | unbox
 | copy_array | copy_sarray
 
 inductive binop
diff --git a/library/init/lean/ir/parser.lean b/library/init/lean/ir/parser.lean
index 1b5cf5d912..fcd9427b32 100644
--- a/library/init/lean/ir/parser.lean
+++ b/library/init/lean/ir/parser.lean
@@ -41,8 +41,6 @@ def parse_unop : parser unop :=
 <|> (keyword "copy_sarray" >> return unop.copy_sarray)
 <|> (keyword "box" >> return unop.box)
 <|> (keyword "unbox" >> return unop.unbox)
-<|> (keyword "box_bignum" >> return unop.box_bignum)
-<|> (keyword "unbox_bignum" >> return unop.unbox_bignum)
 <|> (keyword "cast" >> return unop.cast)
 
 def parse_binop : parser binop :=
diff --git a/library/init/lean/ir/type_check.lean b/library/init/lean/ir/type_check.lean
index 51d82a2941..226021b4e0 100644
--- a/library/init/lean/ir/type_check.lean
+++ b/library/init/lean/ir/type_check.lean
@@ -49,10 +49,8 @@ match op with
 | unop.shared       := t = type.object && r = type.bool
 | unop.copy_array   := t = type.object && r = type.object
 | unop.copy_sarray  := t = type.object && r = type.object
-| unop.box          := t ≠ type.object && r = type.object
-| unop.unbox        := t = type.object && r ≠ type.object
-| unop.unbox_bignum := t = type.object && (r = type.uint32 || r = type.int32)
-| unop.box_bignum   := r = type.object && (t = type.uint32 || t = type.int32)
+| unop.unbox        := t = type.object && (r = type.uint32 || r = type.int32)
+| unop.box          := r = type.object && (t = type.uint32 || t = type.int32)
 | unop.cast         := r ≠ type.object && r ≠ type.object
 
 /-- Return `tt` iff the instruction `x : r := op y z` is type correct where `y z : t` -/