diff --git a/src/Illuminate/Database/Eloquent/Relations/MorphTo.php b/src/Illuminate/Database/Eloquent/Relations/MorphTo.php
index 22d1d4d2c1a2..9fc03bb88165 100644
--- a/src/Illuminate/Database/Eloquent/Relations/MorphTo.php
+++ b/src/Illuminate/Database/Eloquent/Relations/MorphTo.php
@@ -136,7 +136,7 @@ protected function getResultsByType($type)
         $whereIn = $this->whereInMethod($instance, $ownerKey);
 
         return $query->{$whereIn}(
-            $instance->getTable().'.'.$ownerKey, $this->gatherKeysByType($type)
+            $instance->getTable().'.'.$ownerKey, $this->gatherKeysByType($type, $instance->getKeyType())
         )->get();
     }
 
@@ -144,10 +144,17 @@ protected function getResultsByType($type)
      * Gather all of the foreign keys for a given type.
      *
      * @param  string  $type
+     * @param  string  $keyType
      * @return array
      */
-    protected function gatherKeysByType($type)
+    protected function gatherKeysByType($type, $keyType)
     {
+        if ($keyType === 'string') {
+            return array_map(function ($modelId) {
+                return (string) $modelId;
+            }, array_keys($this->dictionary[$type]));
+        }
+
         return array_keys($this->dictionary[$type]);
     }