diff --git a/src/models/User.ts b/src/models/User.ts
index 35bdf4c..fb939d3 100644
--- a/src/models/User.ts
+++ b/src/models/User.ts
@@ -54,7 +54,7 @@ const userSchema = new mongoose.Schema({
  * Password hash middleware.
  */
 userSchema.pre("save", function save(next) {
-  const user = this;
+  const user = this as UserDocument;
   if (!user.isModified("password")) { return next(); }
   bcrypt.genSalt(10, (err, salt) => {
     if (err) { return next(err); }