diff --git a/arith_386.s b/arith_386.s
deleted file mode 100644
index cc50a01..0000000
--- a/arith_386.s
+++ /dev/null
@@ -1,36 +0,0 @@
-// Trampolines to math/big assembly implementations.
-
-#include "textflag.h"
-
-// func addVV(z, x, y []Word) (c Word)
-TEXT ·addVV(SB),NOSPLIT,$0
-	JMP	math∕big·addVV(SB)
-
-// func subVV(z, x, y []Word) (c Word)
-TEXT ·subVV(SB),NOSPLIT,$0
-	JMP	math∕big·subVV(SB)
-
-// func addVW(z, x []Word, y Word) (c Word)
-TEXT ·addVW(SB),NOSPLIT,$0
-	JMP	math∕big·addVW(SB)
-
-// func subVW(z, x []Word, y Word) (c Word)
-TEXT ·subVW(SB),NOSPLIT,$0
-	JMP	math∕big·subVW(SB)
-
-// func shlVU(z, x []Word, s uint) (c Word)
-TEXT ·shlVU(SB),NOSPLIT,$0
-	JMP	math∕big·shlVU(SB)
-
-// func shrVU(z, x []Word, s uint) (c Word)
-TEXT ·shrVU(SB),NOSPLIT,$0
-	JMP	math∕big·shrVU(SB)
-
-// func mulAddVWW(z, x []Word, y, r Word) (c Word)
-TEXT ·mulAddVWW(SB),NOSPLIT,$0
-	JMP	math∕big·mulAddVWW(SB)
-
-// func addMulVVW(z, x []Word, y Word) (c Word)
-TEXT ·addMulVVW(SB),NOSPLIT,$0
-	JMP	math∕big·addMulVVW(SB)
-
diff --git a/arith_amd64.s b/arith_amd64.s
deleted file mode 100644
index 0b79335..0000000
--- a/arith_amd64.s
+++ /dev/null
@@ -1,38 +0,0 @@
-// Trampolines to math/big assembly implementations.
-
-#include "textflag.h"
-
-// func addVV(z, x, y []Word) (c Word)
-TEXT ·addVV(SB),NOSPLIT,$0
-	JMP	math∕big·addVV(SB)
-
-// func subVV(z, x, y []Word) (c Word)
-// (same as addVV except for SBBQ instead of ADCQ and label names)
-TEXT ·subVV(SB),NOSPLIT,$0
-	JMP	math∕big·subVV(SB)
-
-// func addVW(z, x []Word, y Word) (c Word)
-TEXT ·addVW(SB),NOSPLIT,$0
-	JMP	math∕big·addVW(SB)
-
-// func subVW(z, x []Word, y Word) (c Word)
-// (same as addVW except for SUBQ/SBBQ instead of ADDQ/ADCQ and label names)
-TEXT ·subVW(SB),NOSPLIT,$0
-	JMP	math∕big·subVW(SB)
-
-// func shlVU(z, x []Word, s uint) (c Word)
-TEXT ·shlVU(SB),NOSPLIT,$0
-	JMP	math∕big·shlVU(SB)
-
-// func shrVU(z, x []Word, s uint) (c Word)
-TEXT ·shrVU(SB),NOSPLIT,$0
-	JMP	math∕big·shrVU(SB)
-
-// func mulAddVWW(z, x []Word, y, r Word) (c Word)
-TEXT ·mulAddVWW(SB),NOSPLIT,$0
-	JMP	math∕big·mulAddVWW(SB)
-
-// func addMulVVW(z, x []Word, y Word) (c Word)
-TEXT ·addMulVVW(SB),NOSPLIT,$0
-	JMP	math∕big·addMulVVW(SB)
-
diff --git a/arith_arm.s b/arith_arm.s
deleted file mode 100644
index 0ed60f5..0000000
--- a/arith_arm.s
+++ /dev/null
@@ -1,36 +0,0 @@
-// Trampolines to math/big assembly implementations.
-
-#include "textflag.h"
-
-// func addVV(z, x, y []Word) (c Word)
-TEXT ·addVV(SB),NOSPLIT,$0
-	B	math∕big·addVV(SB)
-
-// func subVV(z, x, y []Word) (c Word)
-TEXT ·subVV(SB),NOSPLIT,$0
-	B	math∕big·subVV(SB)
-
-// func addVW(z, x []Word, y Word) (c Word)
-TEXT ·addVW(SB),NOSPLIT,$0
-	B	math∕big·addVW(SB)
-
-// func subVW(z, x []Word, y Word) (c Word)
-TEXT ·subVW(SB),NOSPLIT,$0
-	B	math∕big·subVW(SB)
-
-// func shlVU(z, x []Word, s uint) (c Word)
-TEXT ·shlVU(SB),NOSPLIT,$0
-	B	math∕big·shlVU(SB)
-
-// func shrVU(z, x []Word, s uint) (c Word)
-TEXT ·shrVU(SB),NOSPLIT,$0
-	B	math∕big·shrVU(SB)
-
-// func mulAddVWW(z, x []Word, y, r Word) (c Word)
-TEXT ·mulAddVWW(SB),NOSPLIT,$0
-	B	math∕big·mulAddVWW(SB)
-
-// func addMulVVW(z, x []Word, y Word) (c Word)
-TEXT ·addMulVVW(SB),NOSPLIT,$0
-	B	math∕big·addMulVVW(SB)
-
diff --git a/arith_arm64.s b/arith_arm64.s
deleted file mode 100644
index 0ed60f5..0000000
--- a/arith_arm64.s
+++ /dev/null
@@ -1,36 +0,0 @@
-// Trampolines to math/big assembly implementations.
-
-#include "textflag.h"
-
-// func addVV(z, x, y []Word) (c Word)
-TEXT ·addVV(SB),NOSPLIT,$0
-	B	math∕big·addVV(SB)
-
-// func subVV(z, x, y []Word) (c Word)
-TEXT ·subVV(SB),NOSPLIT,$0
-	B	math∕big·subVV(SB)
-
-// func addVW(z, x []Word, y Word) (c Word)
-TEXT ·addVW(SB),NOSPLIT,$0
-	B	math∕big·addVW(SB)
-
-// func subVW(z, x []Word, y Word) (c Word)
-TEXT ·subVW(SB),NOSPLIT,$0
-	B	math∕big·subVW(SB)
-
-// func shlVU(z, x []Word, s uint) (c Word)
-TEXT ·shlVU(SB),NOSPLIT,$0
-	B	math∕big·shlVU(SB)
-
-// func shrVU(z, x []Word, s uint) (c Word)
-TEXT ·shrVU(SB),NOSPLIT,$0
-	B	math∕big·shrVU(SB)
-
-// func mulAddVWW(z, x []Word, y, r Word) (c Word)
-TEXT ·mulAddVWW(SB),NOSPLIT,$0
-	B	math∕big·mulAddVWW(SB)
-
-// func addMulVVW(z, x []Word, y Word) (c Word)
-TEXT ·addMulVVW(SB),NOSPLIT,$0
-	B	math∕big·addMulVVW(SB)
-
diff --git a/arith_decl.go b/arith_decl.go
index 7659b01..96937df 100644
--- a/arith_decl.go
+++ b/arith_decl.go
@@ -4,13 +4,30 @@
 
 package bigfft
 
-import . "math/big"
+import (
+	"math/big"
+	_ "unsafe"
+)
 
-// implemented in arith_$GOARCH.s
+type Word = big.Word
+
+//go:linkname addVV math/big.addVV
 func addVV(z, x, y []Word) (c Word)
+
+//go:linkname subVV math/big.subVV
 func subVV(z, x, y []Word) (c Word)
+
+//go:linkname addVW math/big.addVW
 func addVW(z, x []Word, y Word) (c Word)
+
+//go:linkname subVW math/big.subVW
 func subVW(z, x []Word, y Word) (c Word)
+
+//go:linkname shlVU math/big.shlVU
 func shlVU(z, x []Word, s uint) (c Word)
+
+//go:linkname mulAddVWW math/big.mulAddVWW
 func mulAddVWW(z, x []Word, y, r Word) (c Word)
+
+//go:linkname addMulVVW math/big.addMulVVW
 func addMulVVW(z, x []Word, y Word) (c Word)
diff --git a/arith_mips64x.s b/arith_mips64x.s
deleted file mode 100644
index 8244388..0000000
--- a/arith_mips64x.s
+++ /dev/null
@@ -1,40 +0,0 @@
-// Trampolines to math/big assembly implementations.
-
-// +build mips64 mips64le
-
-#include "textflag.h"
-
-// func addVV(z, x, y []Word) (c Word)
-TEXT ·addVV(SB),NOSPLIT,$0
-	JMP	math∕big·addVV(SB)
-
-// func subVV(z, x, y []Word) (c Word)
-// (same as addVV except for SBBQ instead of ADCQ and label names)
-TEXT ·subVV(SB),NOSPLIT,$0
-	JMP	math∕big·subVV(SB)
-
-// func addVW(z, x []Word, y Word) (c Word)
-TEXT ·addVW(SB),NOSPLIT,$0
-	JMP	math∕big·addVW(SB)
-
-// func subVW(z, x []Word, y Word) (c Word)
-// (same as addVW except for SUBQ/SBBQ instead of ADDQ/ADCQ and label names)
-TEXT ·subVW(SB),NOSPLIT,$0
-	JMP	math∕big·subVW(SB)
-
-// func shlVU(z, x []Word, s uint) (c Word)
-TEXT ·shlVU(SB),NOSPLIT,$0
-	JMP	math∕big·shlVU(SB)
-
-// func shrVU(z, x []Word, s uint) (c Word)
-TEXT ·shrVU(SB),NOSPLIT,$0
-	JMP	math∕big·shrVU(SB)
-
-// func mulAddVWW(z, x []Word, y, r Word) (c Word)
-TEXT ·mulAddVWW(SB),NOSPLIT,$0
-	JMP	math∕big·mulAddVWW(SB)
-
-// func addMulVVW(z, x []Word, y Word) (c Word)
-TEXT ·addMulVVW(SB),NOSPLIT,$0
-	JMP	math∕big·addMulVVW(SB)
-
diff --git a/arith_mipsx.s b/arith_mipsx.s
deleted file mode 100644
index 6c0e92e..0000000
--- a/arith_mipsx.s
+++ /dev/null
@@ -1,40 +0,0 @@
-// Trampolines to math/big assembly implementations.
-
-// +build mips mipsle
-
-#include "textflag.h"
-
-// func addVV(z, x, y []Word) (c Word)
-TEXT ·addVV(SB),NOSPLIT,$0
-	JMP	math∕big·addVV(SB)
-
-// func subVV(z, x, y []Word) (c Word)
-// (same as addVV except for SBBQ instead of ADCQ and label names)
-TEXT ·subVV(SB),NOSPLIT,$0
-	JMP	math∕big·subVV(SB)
-
-// func addVW(z, x []Word, y Word) (c Word)
-TEXT ·addVW(SB),NOSPLIT,$0
-	JMP	math∕big·addVW(SB)
-
-// func subVW(z, x []Word, y Word) (c Word)
-// (same as addVW except for SUBQ/SBBQ instead of ADDQ/ADCQ and label names)
-TEXT ·subVW(SB),NOSPLIT,$0
-	JMP	math∕big·subVW(SB)
-
-// func shlVU(z, x []Word, s uint) (c Word)
-TEXT ·shlVU(SB),NOSPLIT,$0
-	JMP	math∕big·shlVU(SB)
-
-// func shrVU(z, x []Word, s uint) (c Word)
-TEXT ·shrVU(SB),NOSPLIT,$0
-	JMP	math∕big·shrVU(SB)
-
-// func mulAddVWW(z, x []Word, y, r Word) (c Word)
-TEXT ·mulAddVWW(SB),NOSPLIT,$0
-	JMP	math∕big·mulAddVWW(SB)
-
-// func addMulVVW(z, x []Word, y Word) (c Word)
-TEXT ·addMulVVW(SB),NOSPLIT,$0
-	JMP	math∕big·addMulVVW(SB)
-
diff --git a/arith_ppc64x.s b/arith_ppc64x.s
deleted file mode 100644
index 16c7f15..0000000
--- a/arith_ppc64x.s
+++ /dev/null
@@ -1,38 +0,0 @@
-// Trampolines to math/big assembly implementations.
-
-// +build ppc64 ppc64le
-
-#include "textflag.h"
-
-// func addVV(z, x, y []Word) (c Word)
-TEXT ·addVV(SB),NOSPLIT,$0
-	BR	math∕big·addVV(SB)
-
-// func subVV(z, x, y []Word) (c Word)
-TEXT ·subVV(SB),NOSPLIT,$0
-	BR	math∕big·subVV(SB)
-
-// func addVW(z, x []Word, y Word) (c Word)
-TEXT ·addVW(SB),NOSPLIT,$0
-	BR	math∕big·addVW(SB)
-
-// func subVW(z, x []Word, y Word) (c Word)
-TEXT ·subVW(SB),NOSPLIT,$0
-	BR	math∕big·subVW(SB)
-
-// func shlVU(z, x []Word, s uint) (c Word)
-TEXT ·shlVU(SB),NOSPLIT,$0
-	BR	math∕big·shlVU(SB)
-
-// func shrVU(z, x []Word, s uint) (c Word)
-TEXT ·shrVU(SB),NOSPLIT,$0
-	BR	math∕big·shrVU(SB)
-
-// func mulAddVWW(z, x []Word, y, r Word) (c Word)
-TEXT ·mulAddVWW(SB),NOSPLIT,$0
-	BR	math∕big·mulAddVWW(SB)
-
-// func addMulVVW(z, x []Word, y Word) (c Word)
-TEXT ·addMulVVW(SB),NOSPLIT,$0
-	BR	math∕big·addMulVVW(SB)
-
diff --git a/arith_s390x.s b/arith_s390x.s
deleted file mode 100644
index f72ab05..0000000
--- a/arith_s390x.s
+++ /dev/null
@@ -1,37 +0,0 @@
-
-// Trampolines to math/big assembly implementations.
-
-#include "textflag.h"
-
-// func addVV(z, x, y []Word) (c Word)
-TEXT ·addVV(SB),NOSPLIT,$0
-	BR	math∕big·addVV(SB)
-
-// func subVV(z, x, y []Word) (c Word)
-TEXT ·subVV(SB),NOSPLIT,$0
-	BR	math∕big·subVV(SB)
-
-// func addVW(z, x []Word, y Word) (c Word)
-TEXT ·addVW(SB),NOSPLIT,$0
-	BR	math∕big·addVW(SB)
-
-// func subVW(z, x []Word, y Word) (c Word)
-TEXT ·subVW(SB),NOSPLIT,$0
-	BR	math∕big·subVW(SB)
-
-// func shlVU(z, x []Word, s uint) (c Word)
-TEXT ·shlVU(SB),NOSPLIT,$0
-	BR	math∕big·shlVU(SB)
-
-// func shrVU(z, x []Word, s uint) (c Word)
-TEXT ·shrVU(SB),NOSPLIT,$0
-	BR	math∕big·shrVU(SB)
-
-// func mulAddVWW(z, x []Word, y, r Word) (c Word)
-TEXT ·mulAddVWW(SB),NOSPLIT,$0
-	BR	math∕big·mulAddVWW(SB)
-
-// func addMulVVW(z, x []Word, y Word) (c Word)
-TEXT ·addMulVVW(SB),NOSPLIT,$0
-	BR	math∕big·addMulVVW(SB)
-
diff --git a/fermat_test.go b/fermat_test.go
index f9db5ba..b1105d8 100644
--- a/fermat_test.go
+++ b/fermat_test.go
@@ -2,10 +2,14 @@ package bigfft
 
 import (
 	"fmt"
-	. "math/big"
+	"math/big"
 	"testing"
 )
 
+type (
+	Int = big.Int
+)
+
 // parseHex reads an hex-formatted number modulo 2^bits+1.
 func parseHex(s string, bits int) fermat {
 	z := new(Int)
@@ -35,9 +39,9 @@ func TestFermatShift(t *testing.T) {
 	for i := 0; i < n; i++ {
 		f[i] = Word(rnd.Int63())
 	}
-	b := NewInt(1)
+	b := big.NewInt(1)
 	b = b.Lsh(b, uint(n*_W))
-	b = b.Add(b, NewInt(1))
+	b = b.Add(b, big.NewInt(1))
 	z := make(fermat, len(f)) // Test with uninitialized z.
 	for shift := -2048; shift < 2048; shift++ {
 		z.Shift(f, shift)
@@ -61,9 +65,9 @@ func TestFermatShiftHalf(t *testing.T) {
 	for i := 0; i < n; i++ {
 		f[i] = ^Word(0)
 	}
-	b := NewInt(1)
+	b := big.NewInt(1)
 	b = b.Lsh(b, uint(n*_W))
-	b = b.Add(b, NewInt(1))
+	b = b.Add(b, big.NewInt(1))
 	z := make(fermat, len(f)) // Test with uninitialized z.
 	tmp := make(fermat, len(f))
 	tmp2 := make(fermat, len(f))
diff --git a/fft_test.go b/fft_test.go
index e1e1126..f7fb0cb 100644
--- a/fft_test.go
+++ b/fft_test.go
@@ -2,7 +2,7 @@ package bigfft
 
 import (
 	"fmt"
-	. "math/big"
+	"math/big"
 	"math/rand"
 	"testing"
 )
@@ -342,10 +342,10 @@ func BenchmarkMulFFT_5x20Mb(b *testing.B) { benchmarkMulFFT(b, 5e6, 20e6) }
 func BenchmarkMulFFT_5x50Mb(b *testing.B) { benchmarkMulFFT(b, 5e6, 50e6) }
 
 func TestIssue1(t *testing.T) {
-	e := NewInt(1)
+	e := big.NewInt(1)
 	e.SetBit(e, 132048, 1)
-	e.Sub(e, NewInt(4)) // e == 1<<132048 - 4
-	g := NewInt(0).Set(e)
+	e.Sub(e, big.NewInt(4)) // e == 1<<132048 - 4
+	g := big.NewInt(0).Set(e)
 	e.Mul(e, e)
 	g = Mul(g, g)
 	if g.Cmp(e) != 0 {