diff --git a/test/types/schema.test.ts b/test/types/schema.test.ts
index b0e148afce5..6bf7bcd94d2 100644
--- a/test/types/schema.test.ts
+++ b/test/types/schema.test.ts
@@ -897,3 +897,21 @@ function gh12562() {
     }
   );
 }
+
+function gh12590() {
+  const UserSchema = new Schema({
+    _password: String
+  });
+
+  type User = InferSchemaType<typeof UserSchema>;
+
+  expectType<SchemaType<User>>(UserSchema.path('hashed_password'));
+
+  UserSchema.path('hashed_password').validate(function(v) {
+    expectType<HydratedDocument<User>>(this);
+    if (this._password && this._password.length < 8) {
+      this.invalidate('password', 'Password must be at least 8 characters.');
+    }
+  });
+
+}
diff --git a/types/index.d.ts b/types/index.d.ts
index 97663a46d84..4f7cc0e1393 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -258,8 +258,8 @@ declare module 'mongoose' {
     obj: SchemaDefinition<SchemaDefinitionType<EnforcedDocType>>;
 
     /** Gets/sets schema paths. */
+    path<ResultType extends SchemaType = SchemaType<any, HydratedDocument<DocType, TInstanceMethods>>>(path: string): ResultType;
     path<pathGeneric extends keyof EnforcedDocType>(path: pathGeneric): SchemaType<EnforcedDocType[pathGeneric]>;
-    path<ResultType extends SchemaType = SchemaType>(path: string): ResultType;
     path(path: string, constructor: any): this;
 
     /** Lists all paths and their type in the schema. */
diff --git a/types/schematypes.d.ts b/types/schematypes.d.ts
index 093651d1408..513037cffe5 100644
--- a/types/schematypes.d.ts
+++ b/types/schematypes.d.ts
@@ -188,7 +188,11 @@ declare module 'mongoose' {
     [other: string]: any;
   }
 
-  class SchemaType<T = any> {
+  interface Validator {
+    message?: string; type?: string; validator?: Function
+  }
+
+  class SchemaType<T = any, DocType = any> {
     /** SchemaType constructor */
     constructor(path: string, options?: AnyObject, instance?: string);
 
@@ -270,10 +274,10 @@ declare module 'mongoose' {
     unique(bool: boolean): this;
 
     /** The validators that Mongoose should run to validate properties at this SchemaType's path. */
-    validators: { message?: string; type?: string; validator?: Function }[];
+    validators: Validator[];
 
     /** Adds validator(s) for this document path. */
-    validate(obj: RegExp | Function | any, errorMsg?: string, type?: string): this;
+    validate(obj: RegExp | ((this: DocType, value: any, validatorProperties?: Validator) => any), errorMsg?: string, type?: string): this;
   }
 
   namespace Schema {