diff --git a/src/pkg/Makefile b/src/pkg/Makefile
index 7337951ae5..005c957046 100644
--- a/src/pkg/Makefile
+++ b/src/pkg/Makefile
@@ -23,7 +23,6 @@ DIRS=\
 	archive/tar\
 	asn1\
 	big\
-	bignum\
 	bufio\
 	bytes\
 	cmath\
@@ -64,6 +63,7 @@ DIRS=\
 	encoding/hex\
 	encoding/pem\
 	exec\
+	exp/bignum\
 	exp/datafmt\
 	exp/draw\
 	exp/eval\
diff --git a/src/pkg/bignum/Makefile b/src/pkg/exp/bignum/Makefile
similarity index 74%
rename from src/pkg/bignum/Makefile
rename to src/pkg/exp/bignum/Makefile
index c3dd595316..064cf1eb95 100644
--- a/src/pkg/bignum/Makefile
+++ b/src/pkg/exp/bignum/Makefile
@@ -2,13 +2,13 @@
 # Use of this source code is governed by a BSD-style
 # license that can be found in the LICENSE file.
 
-include ../../Make.$(GOARCH)
+include ../../../Make.$(GOARCH)
 
-TARG=bignum
+TARG=exp/bignum
 GOFILES=\
 	arith.go\
 	bignum.go\
 	integer.go\
 	rational.go\
 
-include ../../Make.pkg
+include ../../../Make.pkg
diff --git a/src/pkg/bignum/arith.go b/src/pkg/exp/bignum/arith.go
similarity index 100%
rename from src/pkg/bignum/arith.go
rename to src/pkg/exp/bignum/arith.go
diff --git a/src/pkg/bignum/arith_amd64.s b/src/pkg/exp/bignum/arith_amd64.s
similarity index 100%
rename from src/pkg/bignum/arith_amd64.s
rename to src/pkg/exp/bignum/arith_amd64.s
diff --git a/src/pkg/bignum/bignum.go b/src/pkg/exp/bignum/bignum.go
similarity index 100%
rename from src/pkg/bignum/bignum.go
rename to src/pkg/exp/bignum/bignum.go
diff --git a/src/pkg/bignum/bignum_test.go b/src/pkg/exp/bignum/bignum_test.go
similarity index 97%
rename from src/pkg/bignum/bignum_test.go
rename to src/pkg/exp/bignum/bignum_test.go
index ade72dd1bc..8db93aa96f 100644
--- a/src/pkg/bignum/bignum_test.go
+++ b/src/pkg/exp/bignum/bignum_test.go
@@ -331,6 +331,16 @@ func TestNatDiv(t *testing.T) {
 	for i := uint(0); i < n; i++ {
 		nat_eq(100+i, p.Div(MulRange(1, i)), MulRange(i+1, n))
 	}
+
+	// a specific test case that exposed a bug in package big
+	test_msg = "NatDivC"
+	x := natFromString("69720375229712477164533808935312303556800", 10, nil)
+	y := natFromString("3099044504245996706400", 10, nil)
+	q := natFromString("22497377864108980962", 10, nil)
+	r := natFromString("0", 10, nil)
+	qc, rc := x.DivMod(y)
+	nat_eq(0, q, qc)
+	nat_eq(1, r, rc)
 }
 
 
diff --git a/src/pkg/bignum/integer.go b/src/pkg/exp/bignum/integer.go
similarity index 100%
rename from src/pkg/bignum/integer.go
rename to src/pkg/exp/bignum/integer.go
diff --git a/src/pkg/bignum/nrdiv_test.go b/src/pkg/exp/bignum/nrdiv_test.go
similarity index 100%
rename from src/pkg/bignum/nrdiv_test.go
rename to src/pkg/exp/bignum/nrdiv_test.go
diff --git a/src/pkg/bignum/rational.go b/src/pkg/exp/bignum/rational.go
similarity index 100%
rename from src/pkg/bignum/rational.go
rename to src/pkg/exp/bignum/rational.go
diff --git a/src/pkg/exp/eval/eval_test.go b/src/pkg/exp/eval/eval_test.go
index 837c4fabdc..1dfdfe1fd6 100644
--- a/src/pkg/exp/eval/eval_test.go
+++ b/src/pkg/exp/eval/eval_test.go
@@ -5,7 +5,7 @@
 package eval
 
 import (
-	"bignum"
+	"exp/bignum"
 	"flag"
 	"fmt"
 	"log"
diff --git a/src/pkg/exp/eval/expr.go b/src/pkg/exp/eval/expr.go
index 81e9ffa935..ea8117d065 100644
--- a/src/pkg/exp/eval/expr.go
+++ b/src/pkg/exp/eval/expr.go
@@ -5,7 +5,7 @@
 package eval
 
 import (
-	"bignum"
+	"exp/bignum"
 	"fmt"
 	"go/ast"
 	"go/token"
diff --git a/src/pkg/exp/eval/expr1.go b/src/pkg/exp/eval/expr1.go
index 0e83053f46..f0a78ac4d6 100644
--- a/src/pkg/exp/eval/expr1.go
+++ b/src/pkg/exp/eval/expr1.go
@@ -4,7 +4,7 @@
 package eval
 
 import (
-	"bignum"
+	"exp/bignum"
 	"log"
 )
 
diff --git a/src/pkg/exp/eval/expr_test.go b/src/pkg/exp/eval/expr_test.go
index 12914fbd54..7efa2069df 100644
--- a/src/pkg/exp/eval/expr_test.go
+++ b/src/pkg/exp/eval/expr_test.go
@@ -5,7 +5,7 @@
 package eval
 
 import (
-	"bignum"
+	"exp/bignum"
 	"testing"
 )
 
diff --git a/src/pkg/exp/eval/stmt.go b/src/pkg/exp/eval/stmt.go
index bb080375a8..bcd81f04cb 100644
--- a/src/pkg/exp/eval/stmt.go
+++ b/src/pkg/exp/eval/stmt.go
@@ -5,7 +5,7 @@
 package eval
 
 import (
-	"bignum"
+	"exp/bignum"
 	"log"
 	"go/ast"
 	"go/token"
diff --git a/src/pkg/exp/eval/type.go b/src/pkg/exp/eval/type.go
index 8a0a2cf2fa..b0fbe21565 100644
--- a/src/pkg/exp/eval/type.go
+++ b/src/pkg/exp/eval/type.go
@@ -5,7 +5,7 @@
 package eval
 
 import (
-	"bignum"
+	"exp/bignum"
 	"go/ast"
 	"go/token"
 	"log"
diff --git a/src/pkg/exp/eval/util.go b/src/pkg/exp/eval/util.go
index 6508346dd9..ffe13e1702 100644
--- a/src/pkg/exp/eval/util.go
+++ b/src/pkg/exp/eval/util.go
@@ -5,7 +5,7 @@
 package eval
 
 import (
-	"bignum"
+	"exp/bignum"
 )
 
 // TODO(austin): Maybe add to bignum in more general form
diff --git a/src/pkg/exp/eval/value.go b/src/pkg/exp/eval/value.go
index 153349c437..dce4bfcf3d 100644
--- a/src/pkg/exp/eval/value.go
+++ b/src/pkg/exp/eval/value.go
@@ -5,7 +5,7 @@
 package eval
 
 import (
-	"bignum"
+	"exp/bignum"
 	"fmt"
 )
 
diff --git a/test/hilbert.go b/test/hilbert.go
index 9438045c86..07db353240 100644
--- a/test/hilbert.go
+++ b/test/hilbert.go
@@ -10,7 +10,7 @@
 
 package main
 
-import Big "bignum"
+import Big "exp/bignum"
 import Fmt "fmt"