diff --git a/compiler/testdata/http/main_durable.go b/compiler/testdata/http/main_durable.go
index 2a52f59..e75eb94 100644
--- a/compiler/testdata/http/main_durable.go
+++ b/compiler/testdata/http/main_durable.go
@@ -5,9 +5,9 @@
 package main
 
 import (
-	http "net/http"
 	coroutine "github.com/stealthrocket/coroutine"
 	fmt "fmt"
+	http "net/http"
 )
 import _types "github.com/stealthrocket/coroutine/types"
 //go:noinline
diff --git a/compiler/vendor.go b/compiler/vendor.go
index a48cd02..249b1c5 100644
--- a/compiler/vendor.go
+++ b/compiler/vendor.go
@@ -19,7 +19,6 @@ const copyConcurrency = 16
 func vendor(newRoot string, pkgs []*packages.Package) error {
 	goroot := runtime.GOROOT()
 
-	var dirs []string
 	var scanErr error
 	packages.Visit(pkgs, func(p *packages.Package) bool {
 		path := filepath.Dir(p.GoFiles[0])
@@ -34,52 +33,14 @@ func vendor(newRoot string, pkgs []*packages.Package) error {
 			scanErr = fmt.Errorf("package %s (%s) is not in GOROOT (%s)", p.PkgPath, path, goroot)
 			return false
 		}
-		dirs = append(dirs, rel)
 		return scanErr == nil
 	}, nil)
 	if scanErr != nil {
 		return scanErr
 	}
 
-	type copyOperation struct{ src, dst string }
-	ops := make(chan copyOperation, 256)
-	var group errgroup.Group
-	group.Go(func() error {
-		for _, rel := range dirs {
-			srcDir := filepath.Join(goroot, rel)
-			dstDir := filepath.Join(newRoot, rel)
-			if err := os.MkdirAll(dstDir, 0755); err != nil {
-				return err
-			}
-			entries, err := os.ReadDir(srcDir)
-			if err != nil {
-				return err
-			}
-			for _, entry := range entries {
-				if entry.IsDir() {
-					continue
-				}
-				name := entry.Name()
-				ops <- copyOperation{
-					src: filepath.Join(srcDir, name),
-					dst: filepath.Join(dstDir, name),
-				}
-			}
-		}
-		close(ops)
-		return nil
-	})
-	for i := 0; i < copyConcurrency; i++ {
-		group.Go(func() error {
-			for op := range ops {
-				if err := copyFile(op.dst, op.src); err != nil {
-					return err
-				}
-			}
-			return nil
-		})
-	}
-	if err := group.Wait(); err != nil {
+	// Copy the entire GOROOT/src directory.
+	if err := copyDir(filepath.Join(newRoot, "src"), filepath.Join(goroot, "src")); err != nil {
 		return err
 	}
 
@@ -101,6 +62,57 @@ func vendor(newRoot string, pkgs []*packages.Package) error {
 	return err
 }
 
+type copyOperation struct{ src, dst string }
+
+func copyDir(dst, src string) error {
+	ops := make(chan copyOperation, 256)
+
+	var group errgroup.Group
+	group.Go(func() error {
+		err := scanDir(dst, src, ops)
+		close(ops)
+		return err
+	})
+	for i := 0; i < copyConcurrency; i++ {
+		group.Go(func() error {
+			for op := range ops {
+				if err := copyFile(op.dst, op.src); err != nil {
+					return err
+				}
+			}
+			return nil
+		})
+	}
+	return group.Wait()
+}
+
+func scanDir(dst, src string, ops chan<- copyOperation) error {
+	if err := os.MkdirAll(dst, 0755); err != nil && !errors.Is(err, os.ErrExist) {
+		return err
+	}
+	entries, err := os.ReadDir(src)
+	if err != nil {
+		return err
+	}
+	for _, entry := range entries {
+		name := entry.Name()
+		fmt.Println(dst, src, name)
+		if entry.IsDir() {
+			dstChild := filepath.Join(dst, name)
+			srcChild := filepath.Join(src, name)
+			if err := scanDir(dstChild, srcChild, ops); err != nil {
+				return err
+			}
+		} else {
+			ops <- copyOperation{
+				src: filepath.Join(src, name),
+				dst: filepath.Join(dst, name),
+			}
+		}
+	}
+	return nil
+}
+
 func copyFile(dst, src string) error {
 	srcFile, err := os.Open(src)
 	if err != nil {