diff --git a/Source/IGListBindingSectionController.h b/Source/IGListBindingSectionController.h
index 482fe348..f66ccc85 100644
--- a/Source/IGListBindingSectionController.h
+++ b/Source/IGListBindingSectionController.h
@@ -47,7 +47,7 @@ NS_ASSUME_NONNULL_BEGIN
  Only when `-diffIdentifier`s match is object equality compared, so you can assume the class is the same, and the
  instance has already been checked.
  */
-@interface IGListBindingSectionController : IGListSectionController<IGListSectionType>
+@interface IGListBindingSectionController<__covariant ObjectType : id<IGListDiffable>> : IGListSectionController<IGListSectionType>
 
 /**
  A data source that transforms a top-level object into view models, and returns cells and sizes for given view models.
@@ -59,6 +59,11 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @property (nonatomic, weak, nullable) id<IGListBindingSectionControllerSelectionDelegate> selectionDelegate;
 
+/**
+ The object currently assigned to the section controller, if any.
+ */
+@property (nonatomic, strong, readonly, nullable) ObjectType object;
+
 /**
  The array of view models created from the data source. Values are changed when the top-level object changes or by
  calling `-updateAnimated:completion:` manually.
diff --git a/Source/IGListBindingSectionController.m b/Source/IGListBindingSectionController.m
index 5dffe5a2..ce1617fd 100644
--- a/Source/IGListBindingSectionController.m
+++ b/Source/IGListBindingSectionController.m
@@ -54,7 +54,11 @@ typedef NS_ENUM(NSInteger, IGListDiffingSectionState) {
         }
         
         oldViewModels = self.viewModels;
-        self.viewModels = [self.dataSource sectionController:self viewModelsForObject:self.object];
+
+        id<IGListDiffable> object = self.object;
+        IGAssert(object != nil, @"Expected IGListBindingSectionController object to be non-nil before updating.");
+        
+        self.viewModels = [self.dataSource sectionController:self viewModelsForObject:object];
         result = IGListDiff(oldViewModels, self.viewModels, IGListDiffEquality);
         
         [result.updates enumerateIndexesUsingBlock:^(NSUInteger oldUpdatedIndex, BOOL *stop) {