diff --git a/go/packages/golist.go b/go/packages/golist.go
index 2675c882..2dcc85e2 100644
--- a/go/packages/golist.go
+++ b/go/packages/golist.go
@@ -13,6 +13,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"reflect"
 	"regexp"
 	"strings"
 	"sync"
@@ -488,6 +489,7 @@ func golistDriverCurrent(cfg *Config, words ...string) (*driverResponse, error)
 	if err != nil {
 		return nil, err
 	}
+	seen := make(map[string]*jsonPackage)
 	// Decode the JSON and convert it to Package form.
 	var response driverResponse
 	for dec := json.NewDecoder(buf); dec.More(); {
@@ -510,6 +512,15 @@ func golistDriverCurrent(cfg *Config, words ...string) (*driverResponse, error)
 			return nil, fmt.Errorf("package missing import path: %+v", p)
 		}
 
+		if old, found := seen[p.ImportPath]; found {
+			if !reflect.DeepEqual(p, old) {
+				return nil, fmt.Errorf("go list repeated package %v with different values", p.ImportPath)
+			}
+			// skip the duplicate
+			continue
+		}
+		seen[p.ImportPath] = p
+
 		pkg := &Package{
 			Name:            p.Name,
 			ID:              p.ImportPath,
diff --git a/go/packages/packages.go b/go/packages/packages.go
index 4e78f341..f3e04f39 100644
--- a/go/packages/packages.go
+++ b/go/packages/packages.go
@@ -437,6 +437,11 @@ func (ld *loader) refine(roots []string, list ...*Package) ([]*Package, error) {
 			lpkg.initial = true
 		}
 	}
+	for i, root := range roots {
+		if initial[i] == nil {
+			return nil, fmt.Errorf("root package %v is missing", root)
+		}
+	}
 
 	// Materialize the import graph.
 
diff --git a/go/packages/packages_test.go b/go/packages/packages_test.go
index 3f800036..275e8899 100644
--- a/go/packages/packages_test.go
+++ b/go/packages/packages_test.go
@@ -1488,6 +1488,31 @@ EOF
 	}
 }
 
+// This test that a simple x test package layout loads correctly.
+// There was a bug in go list where it returned multiple copies of the same
+// package (specifically in this case of golang.org/fake/a), and this triggered
+// a bug in go/packages where it would leave an empty entry in the root package
+// list. This would then cause a nil pointer crash.
+// This bug was triggered by the simple package layout below, and thus this
+// test will make sure the bug remains fixed.
+func TestBasicXTest(t *testing.T) { packagestest.TestAll(t, testBasicXTest) }
+func testBasicXTest(t *testing.T, exporter packagestest.Exporter) {
+	exported := packagestest.Export(t, exporter, []packagestest.Module{{
+		Name: "golang.org/fake",
+		Files: map[string]interface{}{
+			"a/a.go":      `package a;`,
+			"a/a_test.go": `package a_test;`,
+		}}})
+	defer exported.Cleanup()
+
+	exported.Config.Mode = packages.LoadFiles
+	exported.Config.Tests = true
+	_, err := packages.Load(exported.Config, "golang.org/fake/a")
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
 func errorMessages(errors []packages.Error) []string {
 	var msgs []string
 	for _, err := range errors {