diff --git a/src/auto-builder.ts b/src/auto-builder.ts
index 831f602e..ab8dcda6 100644
--- a/src/auto-builder.ts
+++ b/src/auto-builder.ts
@@ -1,5 +1,5 @@
 import _ from "lodash";
-import { Dialect, QueryInterface, QueryTypes, Sequelize } from "sequelize";
+import { ColumnsDescription, Dialect, QueryInterface, QueryTypes, Sequelize } from 'sequelize';
 import { AutoOptions } from ".";
 import { ColumnElementType, ColumnPrecision, DialectOptions, FKRow, FKSpec, TriggerCount } from "./dialects/dialect-options";
 import { dialects } from "./dialects/dialects";
@@ -187,12 +187,11 @@ export class AutoBuilder {
       this.tableData.indexes[makeTableQName(table)] = await this.queryInterface.showIndex(
         { tableName: table.table_name, schema: table.table_schema }) as IndexSpec[];
 
-      // if there is no primaryKey, and `id` field exists, then make id the primaryKey (#480)
+      // if there is no primaryKey, and a single column unique index exists, or an `id` field exists, then make that field the primaryKey (#480)
       if (!_.some(fields, { primaryKey: true })) {
-        const idname = _.keys(fields).find(f => f.toLowerCase() === 'id');
-        const idfield = idname && fields[idname];
-        if (idfield) {
-          idfield.primaryKey = true;
+        const pkField = this.getUniqueIndexField(fields, this.tableData.indexes[makeTableQName(table)]) || this.getIdField(fields);
+        if (pkField) {
+          pkField.primaryKey = true;
         }
       }
 
@@ -207,6 +206,21 @@ export class AutoBuilder {
     }
   }
 
+  private getUniqueIndexField(fields: ColumnsDescription, tableIndexes: IndexSpec[]) {
+    const uniqueIndex = tableIndexes.find(index => index.unique && index.fields.length === 1 );
+    if(uniqueIndex) {
+      const indexColumnName = uniqueIndex.fields[0].attribute.toLowerCase();
+      const fieldName = _.keys(fields).find(f => f.toLowerCase() === indexColumnName);
+      return fieldName && fields[fieldName];
+    }
+  }
+
+
+  private getIdField(fields: ColumnsDescription) {
+    const idname = _.keys(fields).find(f => f.toLowerCase() === 'id');
+   return idname && fields[idname];
+  }
+
   private executeQuery<T>(query: string): Promise<T[]> {
     return this.sequelize.query(query, {
       type: QueryTypes.SELECT,
diff --git a/test/build.test.js b/test/build.test.js
index a1e8280c..b5fa67bb 100644
--- a/test/build.test.js
+++ b/test/build.test.js
@@ -37,8 +37,9 @@ describe(helpers.getTestDialectTeaser("sequelize-auto build"), function() {
 
     auto.build().then(tableData => {
       callback(tableData);
-    }).finally(() => {
       done();
+    }).catch((e) => {
+      done(e);
     })
   }
 
@@ -71,6 +72,9 @@ describe(helpers.getTestDialectTeaser("sequelize-auto build"), function() {
         const fkParents = foreignKeys[isSnakeTables ? 'parents': 'Parents'];
         const fkKids = foreignKeys[isSnakeTables ? 'kids': 'Kids'];
 
+        const paranoidPkColumn = tables[isSnakeTables ? 'paranoid_users': 'ParanoidUsers'].username;
+        expect(paranoidPkColumn.primaryKey).to.equal(true);
+
         if (helpers.getTestDialect() === "sqlite") {
           expect(foreignKeys).to.have.keys(['Kids', 'Parents', 'ParanoidUsers']);
           expect(fkParanoidUsers).to.include.keys(['UserId']);
diff --git a/test/helpers.js b/test/helpers.js
index 2250d352..77bb1d3f 100644
--- a/test/helpers.js
+++ b/test/helpers.js
@@ -66,7 +66,7 @@ module.exports = {
         });
 
         test.ParanoidUser = test.sequelize.define('ParanoidUser', {
-            username: { type: Sequelize.STRING }
+            username: { type: Sequelize.STRING, unique: true }
           },
           {
             paranoid: true,
@@ -74,6 +74,7 @@ module.exports = {
           }
         );
 
+        test.ParanoidUser.removeAttribute('id');
         test.ParanoidUser.belongsTo(test.User);
 
         // test data for relationships across schemas