diff --git a/cmd/errorer.go b/cmd/errorer.go
deleted file mode 100644
index 79db040..0000000
--- a/cmd/errorer.go
+++ /dev/null
@@ -1,85 +0,0 @@
-package errorer
-
-import (
-	"errorer"
-	"flag"
-	"fmt"
-	"io/ioutil"
-	"log"
-	"os"
-	"path/filepath"
-	"strings"
-)
-
-var (
-	typeNames = flag.String("type", "", "comma-separated list of type names; must be set")
-	output    = flag.String("output", "", "output file name; default srcdir/<type>_errors.go")
-)
-
-func main() {
-	flag.Parse()
-
-	if len(*typeNames) == 0 {
-		os.Exit(2)
-	}
-
-	types := strings.Split(*typeNames, ",")
-	// We accept either one directory or a list of files. Which do we have?
-	args := flag.Args()
-	if len(args) == 0 {
-		// Default: process whole package in current directory.
-		args = []string{"."}
-	}
-
-	// Parse the package once.
-	var (
-		dir string
-		g   errorer.Generator
-	)
-	if len(args) == 1 && isDirectory(args[0]) {
-		dir = args[0]
-		g.ParsePackageDir(args[0])
-	} else {
-		dir = filepath.Dir(args[0])
-		g.ParsePackageFiles(args)
-	}
-
-	// Print the header and package clause.
-	g.Printf("// Code generated by \"errorer %s\"; DO NOT EDIT.\n", strings.Join(os.Args[1:], " "))
-	g.Printf("\n")
-	g.Printf("package %s", g.Pkg.GetName())
-	g.Printf("\n")
-	g.Printf("import (\n")
-	g.Printf("\t\"fmt\"\n")           // Used by all methods.
-	g.Printf("\t\"encoding/json\"\n") // Used by all methods.
-	g.Printf("\t\"bytes\"\n")
-	g.Printf(")\n")
-
-	// Run generate for each type.
-	for _, typeName := range types {
-		g.Generate(typeName)
-	}
-
-	// Format the output.
-	src := g.Format()
-
-	// Write to file.
-	outputName := *output
-	if outputName == "" {
-		baseName := fmt.Sprintf("%s_string.go", types[0])
-		outputName = filepath.Join(dir, strings.ToLower(baseName))
-	}
-	err := ioutil.WriteFile(outputName, src, 0644)
-	if err != nil {
-		log.Fatalf("writing output: %s", err)
-	}
-}
-
-// isDirectory reports whether the named file is a directory.
-func isDirectory(name string) bool {
-	info, err := os.Stat(name)
-	if err != nil {
-		log.Fatal(err)
-	}
-	return info.IsDir()
-}
diff --git a/e2e_test.go b/e2e_test.go
index 50442f6..b1be1cd 100644
--- a/e2e_test.go
+++ b/e2e_test.go
@@ -6,7 +6,7 @@
 
 // +build !android
 
-package errorer
+package main
 
 import (
 	"fmt"
@@ -33,7 +33,7 @@ func TestEndToEnd(t *testing.T) {
 	defer os.RemoveAll(dir)
 	// Create stringer in temporary directory.
 	stringer := filepath.Join(dir, "stringer.exe")
-	err = run("go", "build", "-o", stringer, "cmd/errorer.go")
+	err = run("go", "build", "-o", stringer)
 	if err != nil {
 		t.Fatalf("building stringer: %s", err)
 	}
diff --git a/importer18.go b/importer18.go
index cffdf8a..d98925f 100644
--- a/importer18.go
+++ b/importer18.go
@@ -1,6 +1,6 @@
 // +build !go1.9
 
-package errorer
+package main
 
 import (
 	"go/importer"
diff --git a/importer19.go b/importer19.go
index 6a00530..b55419b 100644
--- a/importer19.go
+++ b/importer19.go
@@ -1,5 +1,5 @@
 // +build go1.9
-package errorer
+package main
 
 import (
 	"go/importer"
diff --git a/jsoner.go b/jsoner.go
index 781f8c5..aef7ec7 100644
--- a/jsoner.go
+++ b/jsoner.go
@@ -1,4 +1,4 @@
-package errorer
+package main
 
 import "fmt"
 
diff --git a/stringer.go b/stringer.go
index 76fa4c5..9c8d06d 100644
--- a/stringer.go
+++ b/stringer.go
@@ -1,8 +1,9 @@
 // Adapted from github.com/golang/tools/cmd/stringer
-package errorer
+package main
 
 import (
 	"bytes"
+	"flag"
 	"fmt"
 	"go/ast"
 	"go/build"
@@ -11,13 +12,88 @@ import (
 	"go/parser"
 	"go/token"
 	"go/types"
+	"io/ioutil"
 	"log"
+	"os"
 	"path/filepath"
 	"reflect"
 	"sort"
 	"strings"
 )
 
+var (
+	typeNames = flag.String("type", "", "comma-separated list of type names; must be set")
+	output    = flag.String("output", "", "output file name; default srcdir/<type>_errors.go")
+)
+
+func main() {
+	flag.Parse()
+
+	if len(*typeNames) == 0 {
+		os.Exit(2)
+	}
+
+	types := strings.Split(*typeNames, ",")
+	// We accept either one directory or a list of files. Which do we have?
+	args := flag.Args()
+	if len(args) == 0 {
+		// Default: process whole package in current directory.
+		args = []string{"."}
+	}
+
+	// Parse the package once.
+	var (
+		dir string
+		g   Generator
+	)
+	if len(args) == 1 && isDirectory(args[0]) {
+		dir = args[0]
+		g.ParsePackageDir(args[0])
+	} else {
+		dir = filepath.Dir(args[0])
+		g.ParsePackageFiles(args)
+	}
+
+	// Print the header and package clause.
+	g.Printf("// Code generated by \"errorer %s\"; DO NOT EDIT.\n", strings.Join(os.Args[1:], " "))
+	g.Printf("\n")
+	g.Printf("package %s", g.Pkg.GetName())
+	g.Printf("\n")
+	g.Printf("import (\n")
+	g.Printf("\t\"fmt\"\n")           // Used by all methods.
+	g.Printf("\t\"encoding/json\"\n") // Used by all methods.
+	g.Printf("\t\"bytes\"\n")
+	g.Printf(")\n")
+
+	// Run generate for each type.
+	for _, typeName := range types {
+		g.Generate(typeName)
+	}
+
+	// Format the output.
+	src := g.Format()
+
+	// Write to file.
+	outputName := *output
+	if outputName == "" {
+		baseName := fmt.Sprintf("%s_string.go", types[0])
+		outputName = filepath.Join(dir, strings.ToLower(baseName))
+	}
+	err := ioutil.WriteFile(outputName, src, 0644)
+	if err != nil {
+		log.Fatalf("writing output: %s", err)
+	}
+}
+
+// isDirectory reports whether the named file is a directory.
+func isDirectory(name string) bool {
+	info, err := os.Stat(name)
+	if err != nil {
+		log.Fatal(err)
+	}
+	return info.IsDir()
+}
+
 // Generator holds the state of the analysis. Primarily used to buffer
 // the output for format.Source.
 type Generator struct {
diff --git a/stringer_test.go b/stringer_test.go
index 88e027b..ae9f6b2 100644
--- a/stringer_test.go
+++ b/stringer_test.go
@@ -1,4 +1,4 @@
-package errorer
+package main
 
 import (
 	"strings"