diff --git a/model/DataObject.php b/model/DataObject.php
index 3f642a100..73014946d 100644
--- a/model/DataObject.php
+++ b/model/DataObject.php
@@ -1532,15 +1532,24 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
 		if($fieldPos = strpos($remoteClass, '.')) {
 			return substr($remoteClass, $fieldPos + 1) . 'ID';
 		}
-		
-		$remoteRelations = array_flip(Config::inst()->get($remoteClass, 'has_one'));
+
+		$remoteRelations = Config::inst()->get($remoteClass, 'has_one');
+		if(!is_array($remoteRelations)) {
+			$remoteRelations = array();
+		}
+		$remoteRelations = array_flip($remoteRelations);
 		
 		// look for remote has_one joins on this class or any parent classes
 		foreach(array_reverse(ClassInfo::ancestry($this)) as $class) {
 			if(array_key_exists($class, $remoteRelations)) return $remoteRelations[$class] . 'ID';
 		}
-		
-		return 'ParentID';
+
+		$message = "No has_one found on class '$remoteClass'";
+		if($type == 'has_many') {
+			// include a hint for missing has_many that is missing a has_one
+			$message .= ", the has_many relation from '$this->class' to '$remoteClass' requires a has_one on '$remoteClass'";
+		}
+		throw new Exception($message);
 	}
 	
 	/**