diff --git a/go/tools/gopackagesdriver/packageregistry.go b/go/tools/gopackagesdriver/packageregistry.go
index 92f9eac7..81c1643f 100644
--- a/go/tools/gopackagesdriver/packageregistry.go
+++ b/go/tools/gopackagesdriver/packageregistry.go
@@ -15,6 +15,7 @@
 package main

 import (
+	"os"
 	"fmt"
 	"strings"
 )
@@ -76,6 +77,11 @@ func (pr *PackageRegistry) ResolveImports() error {
 func (pr *PackageRegistry) walk(acc map[string]*FlatPackage, root string) {
 	pkg := pr.packagesByID[root]

+	if pkg == nil {
+		fmt.Fprintf(os.Stderr, "Error: package ID not found %v\n", root)
+		return
+	}
+
 	acc[pkg.ID] = pkg
 	for _, pkgID := range pkg.Imports {
 		if _, ok := acc[pkgID]; !ok {