diff --git a/src/Illuminate/Database/Eloquent/Relations/BelongsToMany.php b/src/Illuminate/Database/Eloquent/Relations/BelongsToMany.php
index 8dfbb9bedf1b..b85e92675b32 100755
--- a/src/Illuminate/Database/Eloquent/Relations/BelongsToMany.php
+++ b/src/Illuminate/Database/Eloquent/Relations/BelongsToMany.php
@@ -194,7 +194,7 @@ protected function addWhereConstraints()
      */
     public function addEagerConstraints(array $models)
     {
-        $this->query->whereIn($this->getQualifiedForeignPivotKeyName(), $this->getKeys($models));
+        $this->query->whereIn($this->getQualifiedForeignPivotKeyName(), $this->getKeys($models, $this->parentKey));
     }
 
     /**
@@ -229,7 +229,7 @@ public function match(array $models, Collection $results, $relation)
         // children back to their parent using the dictionary and the keys on the
         // the parent models. Then we will return the hydrated models back out.
         foreach ($models as $model) {
-            if (isset($dictionary[$key = $model->getKey()])) {
+            if (isset($dictionary[$key = $model->{$this->parentKey}])) {
                 $model->setRelation(
                     $relation, $this->related->newCollection($dictionary[$key])
                 );
diff --git a/src/Illuminate/Database/Eloquent/Relations/Concerns/InteractsWithPivotTable.php b/src/Illuminate/Database/Eloquent/Relations/Concerns/InteractsWithPivotTable.php
index b281cd2c3773..f4a9aef42656 100644
--- a/src/Illuminate/Database/Eloquent/Relations/Concerns/InteractsWithPivotTable.php
+++ b/src/Illuminate/Database/Eloquent/Relations/Concerns/InteractsWithPivotTable.php
@@ -293,7 +293,7 @@ protected function baseAttachRecord($id, $timed)
     {
         $record[$this->relatedPivotKey] = $id;
 
-        $record[$this->foreignPivotKey] = $this->parent->getKey();
+        $record[$this->foreignPivotKey] = $this->parent->{$this->parentKey};
 
         // If the record needs to have creation and update timestamps, we will make
         // them by calling the parent model's "freshTimestamp" method which will
@@ -439,7 +439,7 @@ protected function newPivotQuery()
             call_user_func_array([$query, 'whereIn'], $arguments);
         }
 
-        return $query->where($this->foreignPivotKey, $this->parent->getKey());
+        return $query->where($this->foreignPivotKey, $this->parent->{$this->parentKey});
     }
 
     /**