diff --git a/Masonry/MASCompositeConstraint.h b/Masonry/MASCompositeConstraint.h
index 934c6f16..fa255020 100644
--- a/Masonry/MASCompositeConstraint.h
+++ b/Masonry/MASCompositeConstraint.h
@@ -14,6 +14,8 @@
  */
 @interface MASCompositeConstraint : MASConstraint
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  *	Creates a composite with a predefined array of children
  *
@@ -21,6 +23,8 @@
  *
  *	@return	a composite constraint
  */
-- (id)initWithChildren:(NSArray *)children;
+- (instancetype)initWithChildren:(NSArray *)children;
+
+NS_ASSUME_NONNULL_END
 
 @end
diff --git a/Masonry/MASCompositeConstraint.m b/Masonry/MASCompositeConstraint.m
index 2002a405..6464b174 100644
--- a/Masonry/MASCompositeConstraint.m
+++ b/Masonry/MASCompositeConstraint.m
@@ -18,9 +18,9 @@ @interface MASCompositeConstraint () <MASConstraintDelegate>
 
 @implementation MASCompositeConstraint
 
-- (id)initWithChildren:(NSArray *)children {
+- (instancetype)initWithChildren:(NSArray *)children {
     self = [super init];
-    if (!self) return nil;
+    if (!self) return self;
 
     _childConstraints = [children mutableCopy];
     for (MASConstraint *constraint in _childConstraints) {
diff --git a/Masonry/MASConstraint+Private.h b/Masonry/MASConstraint+Private.h
index ee0fd960..faf4de3d 100644
--- a/Masonry/MASConstraint+Private.h
+++ b/Masonry/MASConstraint+Private.h
@@ -13,6 +13,8 @@
 
 @interface MASConstraint ()
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  *  Whether or not to check for an existing constraint instead of adding constraint
  */
@@ -21,7 +23,7 @@
 /**
  *	Usually MASConstraintMaker but could be a parent MASConstraint
  */
-@property (nonatomic, weak) id<MASConstraintDelegate> delegate;
+@property (nullable, nonatomic, weak) id<MASConstraintDelegate> delegate;
 
 /**
  *  Based on a provided value type, is equal to calling:
@@ -32,11 +34,15 @@
  */
 - (void)setLayoutConstantWithValue:(NSValue *)value;
 
+NS_ASSUME_NONNULL_END
+
 @end
 
 
 @interface MASConstraint (Abstract)
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  *	Sets the constraint relation to given NSLayoutRelation
  *  returns a block which accepts one of the following:
@@ -50,17 +56,23 @@
  */
 - (MASConstraint *)addConstraintWithLayoutAttribute:(NSLayoutAttribute)layoutAttribute;
 
+NS_ASSUME_NONNULL_END
+
 @end
 
 
 @protocol MASConstraintDelegate <NSObject>
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  *	Notifies the delegate when the constraint needs to be replaced with another constraint. For example
  *  A MASViewConstraint may turn into a MASCompositeConstraint when an array is passed to one of the equality blocks
  */
 - (void)constraint:(MASConstraint *)constraint shouldBeReplacedWithConstraint:(MASConstraint *)replacementConstraint;
 
-- (MASConstraint *)constraint:(MASConstraint *)constraint addConstraintWithLayoutAttribute:(NSLayoutAttribute)layoutAttribute;
+- (MASConstraint *)constraint:(nullable MASConstraint *)constraint addConstraintWithLayoutAttribute:(NSLayoutAttribute)layoutAttribute;
+
+NS_ASSUME_NONNULL_END
 
 @end
diff --git a/Masonry/MASConstraint.h b/Masonry/MASConstraint.h
index 6fea79ee..f06e929e 100644
--- a/Masonry/MASConstraint.h
+++ b/Masonry/MASConstraint.h
@@ -15,6 +15,8 @@
  */
 @interface MASConstraint : NSObject
 
+NS_ASSUME_NONNULL_BEGIN
+
 // Chaining Support
 
 /**
@@ -223,6 +225,8 @@
  */
 - (void)uninstall;
 
+NS_ASSUME_NONNULL_END
+
 @end
 
 
@@ -252,6 +256,8 @@
 
 @interface MASConstraint (AutoboxingSupport)
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  *  Aliases to corresponding relation methods (for shorthand macros)
  *  Also needed to aid autocompletion
@@ -265,4 +271,6 @@
  */
 - (MASConstraint * (^)(id offset))mas_offset;
 
+NS_ASSUME_NONNULL_END
+
 @end
diff --git a/Masonry/MASConstraint.m b/Masonry/MASConstraint.m
index b8841e58..3a5ad368 100644
--- a/Masonry/MASConstraint.m
+++ b/Masonry/MASConstraint.m
@@ -17,7 +17,7 @@ @implementation MASConstraint
 
 #pragma mark - Init
 
-- (id)init {
+- (instancetype)init {
 	NSAssert(![self isMemberOfClass:[MASConstraint class]], @"MASConstraint is an abstract class, you should not instantiate it directly.");
 	return [super init];
 }
diff --git a/Masonry/MASConstraintMaker.h b/Masonry/MASConstraintMaker.h
index 9a0bc8df..6034524d 100644
--- a/Masonry/MASConstraintMaker.h
+++ b/Masonry/MASConstraintMaker.h
@@ -47,6 +47,8 @@ typedef NS_OPTIONS(NSInteger, MASAttribute) {
  */
 @interface MASConstraintMaker : NSObject
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  *	The following properties return a new MASViewConstraint
  *  with the first item set to the makers associated view and the appropriate MASViewAttribute
@@ -124,7 +126,7 @@ typedef NS_OPTIONS(NSInteger, MASAttribute) {
  *
  *	@return	a new MASConstraintMaker
  */
-- (id)initWithView:(MAS_VIEW *)view;
+- (instancetype)initWithView:(MAS_VIEW *)view;
 
 /**
  *	Calls install method on any MASConstraints which have been created by this maker
@@ -135,4 +137,6 @@ typedef NS_OPTIONS(NSInteger, MASAttribute) {
 
 - (MASConstraint * (^)(dispatch_block_t))group;
 
+NS_ASSUME_NONNULL_END
+
 @end
diff --git a/Masonry/MASConstraintMaker.m b/Masonry/MASConstraintMaker.m
index 26d377be..d6c6b962 100644
--- a/Masonry/MASConstraintMaker.m
+++ b/Masonry/MASConstraintMaker.m
@@ -22,9 +22,9 @@ @interface MASConstraintMaker () <MASConstraintDelegate>
 
 @implementation MASConstraintMaker
 
-- (id)initWithView:(MAS_VIEW *)view {
+- (instancetype)initWithView:(MAS_VIEW *)view {
     self = [super init];
-    if (!self) return nil;
+    if (!self) return self;
     
     self.view = view;
     self.constraints = NSMutableArray.new;
diff --git a/Masonry/MASLayoutConstraint.h b/Masonry/MASLayoutConstraint.h
index 699041cb..0faf8e84 100644
--- a/Masonry/MASLayoutConstraint.h
+++ b/Masonry/MASLayoutConstraint.h
@@ -14,9 +14,13 @@
  */
 @interface MASLayoutConstraint : NSLayoutConstraint
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  *	a key to associate with this constraint
  */
 @property (nonatomic, strong) id mas_key;
 
+NS_ASSUME_NONNULL_END
+
 @end
diff --git a/Masonry/MASViewAttribute.h b/Masonry/MASViewAttribute.h
index 601c25d1..6a8a2b7e 100644
--- a/Masonry/MASViewAttribute.h
+++ b/Masonry/MASViewAttribute.h
@@ -14,15 +14,17 @@
  */
 @interface MASViewAttribute : NSObject
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  *  The view which the reciever relates to. Can be nil if item is not a view.
  */
-@property (nonatomic, weak, readonly) MAS_VIEW *view;
+@property (nullable, nonatomic, weak, readonly) MAS_VIEW *view;
 
 /**
  *  The item which the reciever relates to.
  */
-@property (nonatomic, weak, readonly) id item;
+@property (nullable, nonatomic, weak, readonly) id item;
 
 /**
  *  The attribute which the reciever relates to
@@ -32,12 +34,12 @@
 /**
  *  Convenience initializer.
  */
-- (id)initWithView:(MAS_VIEW *)view layoutAttribute:(NSLayoutAttribute)layoutAttribute;
+- (instancetype)initWithView:(nullable MAS_VIEW *)view layoutAttribute:(NSLayoutAttribute)layoutAttribute;
 
 /**
  *  The designated initializer.
  */
-- (id)initWithView:(MAS_VIEW *)view item:(id)item layoutAttribute:(NSLayoutAttribute)layoutAttribute;
+- (instancetype)initWithView:(nullable MAS_VIEW *)view item:(id)item layoutAttribute:(NSLayoutAttribute)layoutAttribute;
 
 /**
  *	Determine whether the layoutAttribute is a size attribute
@@ -46,4 +48,6 @@
  */
 - (BOOL)isSizeAttribute;
 
+NS_ASSUME_NONNULL_END
+
 @end
diff --git a/Masonry/MASViewAttribute.m b/Masonry/MASViewAttribute.m
index e573e8bd..d10d254b 100644
--- a/Masonry/MASViewAttribute.m
+++ b/Masonry/MASViewAttribute.m
@@ -10,14 +10,14 @@
 
 @implementation MASViewAttribute
 
-- (id)initWithView:(MAS_VIEW *)view layoutAttribute:(NSLayoutAttribute)layoutAttribute {
+- (instancetype)initWithView:(MAS_VIEW *)view layoutAttribute:(NSLayoutAttribute)layoutAttribute {
     self = [self initWithView:view item:view layoutAttribute:layoutAttribute];
     return self;
 }
 
-- (id)initWithView:(MAS_VIEW *)view item:(id)item layoutAttribute:(NSLayoutAttribute)layoutAttribute {
+- (instancetype)initWithView:(MAS_VIEW *)view item:(id)item layoutAttribute:(NSLayoutAttribute)layoutAttribute {
     self = [super init];
-    if (!self) return nil;
+    if (!self) return self;
     
     _view = view;
     _item = item;
diff --git a/Masonry/MASViewConstraint.h b/Masonry/MASViewConstraint.h
index ec390d15..2da216c7 100644
--- a/Masonry/MASViewConstraint.h
+++ b/Masonry/MASViewConstraint.h
@@ -17,6 +17,8 @@
  */
 @interface MASViewConstraint : MASConstraint <NSCopying>
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  *	First item/view and first attribute of the NSLayoutConstraint
  */
@@ -34,7 +36,7 @@
  *
  *	@return	a new view constraint
  */
-- (id)initWithFirstViewAttribute:(MASViewAttribute *)firstViewAttribute;
+- (instancetype)initWithFirstViewAttribute:(MASViewAttribute *)firstViewAttribute;
 
 /**
  *  Returns all MASViewConstraints installed with this view as a first item.
@@ -45,4 +47,6 @@
  */
 + (NSArray *)installedConstraintsForView:(MAS_VIEW *)view;
 
+NS_ASSUME_NONNULL_END
+
 @end
diff --git a/Masonry/MASViewConstraint.m b/Masonry/MASViewConstraint.m
index af3f0b44..10860a04 100644
--- a/Masonry/MASViewConstraint.m
+++ b/Masonry/MASViewConstraint.m
@@ -52,9 +52,9 @@ @interface MASViewConstraint ()
 
 @implementation MASViewConstraint
 
-- (id)initWithFirstViewAttribute:(MASViewAttribute *)firstViewAttribute {
+- (instancetype)initWithFirstViewAttribute:(MASViewAttribute *)firstViewAttribute {
     self = [super init];
-    if (!self) return nil;
+    if (!self) return self;
     
     _firstViewAttribute = firstViewAttribute;
     self.layoutPriority = MASLayoutPriorityRequired;
@@ -65,7 +65,7 @@ - (id)initWithFirstViewAttribute:(MASViewAttribute *)firstViewAttribute {
 
 #pragma mark - NSCoping
 
-- (id)copyWithZone:(NSZone __unused *)zone {
+- (instancetype)copyWithZone:(NSZone __unused *)zone {
     MASViewConstraint *constraint = [[MASViewConstraint alloc] initWithFirstViewAttribute:self.firstViewAttribute];
     constraint.layoutConstant = self.layoutConstant;
     constraint.layoutRelation = self.layoutRelation;
diff --git a/Masonry/NSArray+MASAdditions.h b/Masonry/NSArray+MASAdditions.h
index 587618d9..bb2f69ca 100644
--- a/Masonry/NSArray+MASAdditions.h
+++ b/Masonry/NSArray+MASAdditions.h
@@ -17,6 +17,8 @@ typedef NS_ENUM(NSUInteger, MASAxisType) {
 
 @interface NSArray (MASAdditions)
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  *  Creates a MASConstraintMaker with each view in the callee.
  *  Any constraints defined are added to the view or the appropriate superview once the block has finished executing on each view
@@ -69,4 +71,6 @@ typedef NS_ENUM(NSUInteger, MASAxisType) {
  */
 - (void)mas_distributeViewsAlongAxis:(MASAxisType)axisType withFixedItemLength:(CGFloat)fixedItemLength leadSpacing:(CGFloat)leadSpacing tailSpacing:(CGFloat)tailSpacing;
 
+NS_ASSUME_NONNULL_END
+
 @end
diff --git a/Masonry/NSArray+MASShorthandAdditions.h b/Masonry/NSArray+MASShorthandAdditions.h
index 8b473697..18e2d6dd 100644
--- a/Masonry/NSArray+MASShorthandAdditions.h
+++ b/Masonry/NSArray+MASShorthandAdditions.h
@@ -16,10 +16,14 @@
  */
 @interface NSArray (MASShorthandAdditions)
 
+NS_ASSUME_NONNULL_BEGIN
+
 - (NSArray *)makeConstraints:(void(^)(MASConstraintMaker *make))block;
 - (NSArray *)updateConstraints:(void(^)(MASConstraintMaker *make))block;
 - (NSArray *)remakeConstraints:(void(^)(MASConstraintMaker *make))block;
 
+NS_ASSUME_NONNULL_END
+
 @end
 
 @implementation NSArray (MASShorthandAdditions)
diff --git a/Masonry/View+MASAdditions.h b/Masonry/View+MASAdditions.h
index 00477c1c..7651bf26 100644
--- a/Masonry/View+MASAdditions.h
+++ b/Masonry/View+MASAdditions.h
@@ -16,6 +16,8 @@
  */
 @interface MAS_VIEW (MASAdditions)
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  *	following properties return a new MASViewAttribute with current view and appropriate NSLayoutAttribute
  */
@@ -72,7 +74,7 @@
  *
  *	@return	returns nil if common superview could not be found
  */
-- (instancetype)mas_closestCommonSuperview:(MAS_VIEW *)view;
+- (nullable instancetype)mas_closestCommonSuperview:(MAS_VIEW *)view;
 
 /**
  *  Creates a MASConstraintMaker with the callee view.
@@ -106,4 +108,6 @@
  */
 - (NSArray *)mas_remakeConstraints:(void(NS_NOESCAPE ^)(MASConstraintMaker *make))block;
 
+NS_ASSUME_NONNULL_END
+
 @end
diff --git a/Masonry/View+MASShorthandAdditions.h b/Masonry/View+MASShorthandAdditions.h
index 8e375ee3..6fddae77 100644
--- a/Masonry/View+MASShorthandAdditions.h
+++ b/Masonry/View+MASShorthandAdditions.h
@@ -16,6 +16,8 @@
  */
 @interface MAS_VIEW (MASShorthandAdditions)
 
+NS_ASSUME_NONNULL_BEGIN
+
 @property (nonatomic, strong, readonly) MASViewAttribute *left;
 @property (nonatomic, strong, readonly) MASViewAttribute *top;
 @property (nonatomic, strong, readonly) MASViewAttribute *right;
@@ -64,6 +66,8 @@
 - (NSArray *)updateConstraints:(void(^)(MASConstraintMaker *make))block;
 - (NSArray *)remakeConstraints:(void(^)(MASConstraintMaker *make))block;
 
+NS_ASSUME_NONNULL_END
+
 @end
 
 #define MAS_ATTR_FORWARD(attr)  \
diff --git a/Masonry/ViewController+MASAdditions.h b/Masonry/ViewController+MASAdditions.h
index 564654af..e1a38a4b 100644
--- a/Masonry/ViewController+MASAdditions.h
+++ b/Masonry/ViewController+MASAdditions.h
@@ -14,6 +14,8 @@
 
 @interface MAS_VIEW_CONTROLLER (MASAdditions)
 
+NS_ASSUME_NONNULL_BEGIN
+
 /**
  *	following properties return a new MASViewAttribute with appropriate UILayoutGuide and NSLayoutAttribute
  */
@@ -24,6 +26,8 @@
 @property (nonatomic, strong, readonly) MASViewAttribute *mas_bottomLayoutGuideTop NS_DEPRECATED_IOS(8.0, 11.0);
 @property (nonatomic, strong, readonly) MASViewAttribute *mas_bottomLayoutGuideBottom NS_DEPRECATED_IOS(8.0, 11.0);
 
+NS_ASSUME_NONNULL_END
+
 @end
 
 #endif