diff --git a/cmd/compilebench/main.go b/cmd/compilebench/main.go
index d2cd70b2..4d3b74ef 100644
--- a/cmd/compilebench/main.go
+++ b/cmd/compilebench/main.go
@@ -67,9 +67,9 @@ package main
 
 import (
 	"bytes"
+	"encoding/json"
 	"flag"
 	"fmt"
-	"go/build"
 	"io/ioutil"
 	"log"
 	"os"
@@ -144,6 +144,7 @@ func main() {
 		log.Fatalf("%s env GOROOT: %v", *flagGoCmd, err)
 	}
 	goroot = strings.TrimSpace(string(s))
+	os.Setenv("GOROOT", goroot) // for any subcommands
 
 	compiler = *flagCompiler
 	if compiler == "" {
@@ -250,11 +251,28 @@ func runBuild(name, dir string, count int) {
 		return
 	}
 
-	pkg, err := build.Import(dir, ".", 0)
+	// Make sure dependencies needed by go tool compile are installed to GOROOT/pkg.
+	out, err := exec.Command(*flagGoCmd, "build", "-i", dir).CombinedOutput()
 	if err != nil {
-		log.Print(err)
+		log.Printf("go build -i %s: %v\n%s", dir, err, out)
 		return
 	}
+
+	// Find dir and source file list.
+	var pkg struct {
+		Dir     string
+		GoFiles []string
+	}
+	out, err = exec.Command(*flagGoCmd, "list", "-json", dir).Output()
+	if err != nil {
+		log.Printf("go list -json %s: %v\n", dir, err)
+		return
+	}
+	if err := json.Unmarshal(out, &pkg); err != nil {
+		log.Printf("go list -json %s: unmarshal: %v", dir, err)
+		return
+	}
+
 	args := []string{"-o", "_compilebench_.o"}
 	if is6g {
 		*flagMemprofilerate = -1