diff --git a/SSPullToRefresh/SSPullToRefreshDefaultContentView.h b/SSPullToRefresh/SSPullToRefreshDefaultContentView.h
index 13c1894..c5dede9 100644
--- a/SSPullToRefresh/SSPullToRefreshDefaultContentView.h
+++ b/SSPullToRefresh/SSPullToRefreshDefaultContentView.h
@@ -8,6 +8,8 @@
 
 #import "SSPullToRefreshView.h"
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface SSPullToRefreshDefaultContentView : UIView <SSPullToRefreshContentView>
 
 @property (nonatomic, readonly) UILabel *statusLabel;
@@ -15,3 +17,5 @@
 @property (nonatomic, readonly) UIActivityIndicatorView *activityIndicatorView;
 
 @end
+
+NS_ASSUME_NONNULL_END
diff --git a/SSPullToRefresh/SSPullToRefreshSimpleContentView.h b/SSPullToRefresh/SSPullToRefreshSimpleContentView.h
index e0e8924..085eade 100644
--- a/SSPullToRefresh/SSPullToRefreshSimpleContentView.h
+++ b/SSPullToRefresh/SSPullToRefreshSimpleContentView.h
@@ -8,9 +8,13 @@
 
 #import "SSPullToRefreshView.h"
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface SSPullToRefreshSimpleContentView : UIView <SSPullToRefreshContentView>
 
 @property (nonatomic, readonly) UILabel *statusLabel;
 @property (nonatomic, readonly) UIActivityIndicatorView *activityIndicatorView;
 
 @end
+
+NS_ASSUME_NONNULL_END
diff --git a/SSPullToRefresh/SSPullToRefreshView.h b/SSPullToRefresh/SSPullToRefreshView.h
index e874cdd..b5110e2 100644
--- a/SSPullToRefresh/SSPullToRefreshView.h
+++ b/SSPullToRefresh/SSPullToRefreshView.h
@@ -66,6 +66,8 @@ typedef NS_ENUM(NSUInteger, SSPullToRefreshViewStyle) {
 @protocol SSPullToRefreshViewDelegate;
 @protocol SSPullToRefreshContentView;
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface SSPullToRefreshView : UIView
 
 /**
@@ -105,7 +107,7 @@ typedef NS_ENUM(NSUInteger, SSPullToRefreshViewStyle) {
 
  @see initWithScrollView:delegate:
  */
-@property (nonatomic, assign, readonly) UIScrollView *scrollView;
+@property (nonatomic, weak, readonly, nullable) UIScrollView *scrollView;
 
 /**
  The delegate is sent messages when the pull to refresh view starts loading. This is automatically set with `initWithScrollView:delegate:`.
@@ -113,7 +115,7 @@ typedef NS_ENUM(NSUInteger, SSPullToRefreshViewStyle) {
  @see initWithScrollView:delegate:
  @see SSPullToRefreshViewDelegate
  */
-@property (nonatomic, weak) id<SSPullToRefreshViewDelegate> delegate;
+@property (nonatomic, weak, nullable) id<SSPullToRefreshViewDelegate> delegate;
 
 /**
  The state of the pull to refresh view.
@@ -156,13 +158,13 @@ typedef NS_ENUM(NSUInteger, SSPullToRefreshViewStyle) {
  animate down the pull to refresh view to show that it's loading.
  */
 - (void)startLoadingAndExpand:(BOOL)shouldExpand animated:(BOOL)animated;
-- (void)startLoadingAndExpand:(BOOL)shouldExpand animated:(BOOL)animated completion:(void(^)())block;
+- (void)startLoadingAndExpand:(BOOL)shouldExpand animated:(BOOL)animated completion:(nullable void(^)(void))block;
 
 /**
  Call this when you finish loading.
  */
 - (void)finishLoading;
-- (void)finishLoadingAnimated:(BOOL)animated completion:(void(^)())block;
+- (void)finishLoadingAnimated:(BOOL)animated completion:(nullable void(^)(void))block;
 
 /**
  Manually update the last updated at time. This will automatically get called when the pull to refresh view finishes laoding.
@@ -240,3 +242,5 @@ typedef NS_ENUM(NSUInteger, SSPullToRefreshViewStyle) {
 - (void)setLastUpdatedAt:(NSDate *)date withPullToRefreshView:(SSPullToRefreshView *)view;
 
 @end
+
+NS_ASSUME_NONNULL_END
diff --git a/SSPullToRefresh/SSPullToRefreshView.m b/SSPullToRefresh/SSPullToRefreshView.m
index dd35173..c8b9318 100644
--- a/SSPullToRefresh/SSPullToRefreshView.m
+++ b/SSPullToRefresh/SSPullToRefreshView.m
@@ -194,7 +194,7 @@ - (void)startLoadingAndExpand:(BOOL)shouldExpand animated:(BOOL)animated {
 	[self startLoadingAndExpand:shouldExpand animated:animated completion:nil];
 }
 
-- (void)startLoadingAndExpand:(BOOL)shouldExpand animated:(BOOL)animated completion:(void(^)())block {
+- (void)startLoadingAndExpand:(BOOL)shouldExpand animated:(BOOL)animated completion:(void(^)(void))block {
 	// If we're not loading, this method has no effect
     if (self.state == SSPullToRefreshViewStateLoading) {
 		return;
@@ -209,7 +209,7 @@ - (void)finishLoading {
 	[self finishLoadingAnimated:YES completion:nil];
 }
 
-- (void)finishLoadingAnimated:(BOOL)animated completion:(void(^)())block {
+- (void)finishLoadingAnimated:(BOOL)animated completion:(void(^)(void))block {
 	// If we're not loading, this method has no effect
     if (self.state != SSPullToRefreshViewStateLoading) {
 		return;