diff --git a/build/context.go b/build/context.go
index b537047..52921d8 100644
--- a/build/context.go
+++ b/build/context.go
@@ -5,13 +5,14 @@ import (
 	"fmt"
 	"go/types"
 
+	"golang.org/x/tools/go/packages"
+
 	"github.com/mmcloughlin/avo/attr"
 	"github.com/mmcloughlin/avo/buildtags"
 	"github.com/mmcloughlin/avo/gotypes"
 	"github.com/mmcloughlin/avo/ir"
 	"github.com/mmcloughlin/avo/operand"
 	"github.com/mmcloughlin/avo/reg"
-	"golang.org/x/tools/go/packages"
 )
 
 // Context maintains state for incrementally building an avo File.
diff --git a/build/zmov.go b/build/zmov.go
index bfd9b08..ca9bb55 100644
--- a/build/zmov.go
+++ b/build/zmov.go
@@ -3,8 +3,9 @@
 package build
 
 import (
-	"github.com/mmcloughlin/avo/operand"
 	"go/types"
+
+	"github.com/mmcloughlin/avo/operand"
 )
 
 func (c *Context) mov(a, b operand.Op, an, bn int, t *types.Basic) {
diff --git a/internal/gen/ctors.go b/internal/gen/ctors.go
index 79d3627..eeb75d7 100644
--- a/internal/gen/ctors.go
+++ b/internal/gen/ctors.go
@@ -27,6 +27,7 @@ func (c *ctors) Generate(is []inst.Instruction) ([]byte, error) {
 	c.Printf("package x86\n\n")
 	c.Printf("import (\n")
 	c.Printf("\t\"errors\"\n")
+	c.NL()
 	c.Printf("\tintrep \"%s/ir\"\n", pkg)
 	c.Printf("\t\"%s/reg\"\n", pkg)
 	c.Printf("\t\"%s/operand\"\n", pkg)
diff --git a/internal/gen/ctorstest.go b/internal/gen/ctorstest.go
index 844a495..297e9fe 100644
--- a/internal/gen/ctorstest.go
+++ b/internal/gen/ctorstest.go
@@ -25,6 +25,7 @@ func (c *ctorstest) Generate(is []inst.Instruction) ([]byte, error) {
 	c.Printf("import (\n")
 	c.Printf("\t\"testing\"\n")
 	c.Printf("\t\"math\"\n")
+	c.NL()
 	c.Printf("\t\"%s/reg\"\n", pkg)
 	c.Printf("\t\"%s/operand\"\n", pkg)
 	c.Printf(")\n\n")
diff --git a/internal/gen/gen_test.go b/internal/gen/gen_test.go
index c369fa1..b497d5d 100644
--- a/internal/gen/gen_test.go
+++ b/internal/gen/gen_test.go
@@ -3,7 +3,7 @@ package gen
 import "testing"
 
 func TestBuilderInterfaces(t *testing.T) {
-	var _ = []Builder{
+	_ = []Builder{
 		NewAsmTest,
 		NewGoData,
 		NewGoDataTest,
diff --git a/internal/gen/mov.go b/internal/gen/mov.go
index 4162f05..cf8c232 100644
--- a/internal/gen/mov.go
+++ b/internal/gen/mov.go
@@ -28,6 +28,7 @@ func (m *mov) Generate(is []inst.Instruction) ([]byte, error) {
 
 	m.Printf("import (\n")
 	m.Printf("\t\"go/types\"\n")
+	m.NL()
 	m.Printf("\t\"%s/operand\"\n", pkg)
 	m.Printf(")\n\n")
 
diff --git a/script/bootstrap b/script/bootstrap
index 8a589bf..ba5973f 100755
--- a/script/bootstrap
+++ b/script/bootstrap
@@ -20,3 +20,6 @@ go get -u github.com/dlespiau/covertool
 
 # asmfmt for enforcing assembly style
 go get -u github.com/klauspost/asmfmt/cmd/asmfmt
+
+# gofumports for stricter formatting
+go get -u mvdan.cc/gofumpt/gofumports
diff --git a/script/fmt b/script/fmt
new file mode 100755
index 0000000..80ff752
--- /dev/null
+++ b/script/fmt
@@ -0,0 +1,15 @@
+#!/bin/bash -ex
+
+repo="github.com/mmcloughlin/avo"
+
+# Files to apply formatting to. Exclude stadtx since some of it was imported
+# from the original repo.
+files=$(find . -name '*.go' -not -path '*/stadtx/*')
+
+# Remove blank lines in import blocks. This will force formatting to group
+# imports correctly.
+sed -i.fmtbackup '/^import (/,/)/ { /^$$/ d; }' ${files}
+find . -name '*.fmtbackup' -delete
+
+# gofumports is goimports with stricter formatting.
+gofumports -w -local ${repo} ${files}
diff --git a/script/lint b/script/lint
index fe8922a..de47561 100755
--- a/script/lint
+++ b/script/lint
@@ -4,6 +4,10 @@
 ./script/generate
 test -z "$(git status --porcelain)"
 
+# Still clean after formatting.
+./script/fmt
+test -z "$(git status --porcelain)"
+
 # And it's still clean after asmfmt.
 # Note: we want to confirm we agree with asmfmt without actually depending on it.
 find . -name '*.s' | xargs asmfmt -w
diff --git a/x86/zctors.go b/x86/zctors.go
index 0101d1a..816c0d1 100644
--- a/x86/zctors.go
+++ b/x86/zctors.go
@@ -4,6 +4,7 @@ package x86
 
 import (
 	"errors"
+
 	intrep "github.com/mmcloughlin/avo/ir"
 	"github.com/mmcloughlin/avo/operand"
 	"github.com/mmcloughlin/avo/reg"
diff --git a/x86/zctors_test.go b/x86/zctors_test.go
index b8cebc7..1c70339 100644
--- a/x86/zctors_test.go
+++ b/x86/zctors_test.go
@@ -3,10 +3,11 @@
 package x86
 
 import (
-	"github.com/mmcloughlin/avo/operand"
-	"github.com/mmcloughlin/avo/reg"
 	"math"
 	"testing"
+
+	"github.com/mmcloughlin/avo/operand"
+	"github.com/mmcloughlin/avo/reg"
 )
 
 func TestADCBValidForms(t *testing.T) {