only delete inferred otherKey if different

lib/associations/belongs-to-many.js

@@ -158,21 +158,23 @@ module.exports = (function() {
       }
     }
 
-    if (this.through) {
-      this.throughModel = this.through.model;
-    }
-
     if (this.paired) {
       if (this.otherKeyDefault) {
         this.otherKey = this.paired.foreignKey;
       }
       if (this.paired.otherKeyDefault) {
         // If paired otherKey was inferred we should make sure to clean it up before adding a new one that matches the foreignKey
-        delete this.through.model.rawAttributes[this.paired.otherKey];
+        if (this.paired.otherKey !== this.foreignKey) {
+          delete this.through.model.rawAttributes[this.paired.otherKey];
+        }
         this.paired.otherKey = this.foreignKey;
       }
     }
 
+    if (this.through) {
+      this.throughModel = this.through.model;
+    }
+
     this.options.tableName = this.combinedName = (this.through.model === Object(this.through.model) ? this.through.model.tableName : this.through.model);
 
     if (this.as) {