diff --git a/gopmod/module.go b/gopmod/module.go
index 9a5e46f..1fe3007 100644
--- a/gopmod/module.go
+++ b/gopmod/module.go
@@ -17,6 +17,7 @@
 package gopmod
 
 import (
+	"fmt"
 	"log"
 	"path/filepath"
 	"runtime"
@@ -130,7 +131,7 @@ func (p *Module) lookupExternPkg(pkgPath string) (pkg *Package, err error) {
 			return
 		}
 	}
-	err = &mod.MissingPkgError{Path: pkgPath}
+	err = &MissingError{Path: pkgPath}
 	return
 }
 
@@ -210,4 +211,13 @@ func loadModFrom(mod module.Version, mode mod.Mode) (p *Module, err error) {
 	return Load(dir, mode)
 }
 
+type MissingError struct {
+	Path string
+}
+
+func (e *MissingError) Error() string {
+	return fmt.Sprintf(`no required module provides package %v; to add it:
+	gop get %v`, e.Path, e.Path)
+}
+
 // -----------------------------------------------------------------------------
diff --git a/mod.go b/mod.go
index cb0225c..17ff88e 100644
--- a/mod.go
+++ b/mod.go
@@ -17,7 +17,6 @@
 package mod
 
 import (
-	"fmt"
 	"os"
 	"path/filepath"
 	"strings"
@@ -69,13 +68,4 @@ func GOMOD(dir string) (file string, err error) {
 	return GOPMOD(dir, GoModOnly)
 }
 
-type MissingPkgError struct {
-	Path string
-}
-
-func (e *MissingPkgError) Error() string {
-	return fmt.Sprintf(`no required module provides package %v; to add it:
-	go get %v`, e.Path, e.Path)
-}
-
 // -----------------------------------------------------------------------------