diff --git a/BRYHTMLParser/HTMLNode.h b/BRYHTMLParser/HTMLNode.h
index fd79e82..f9e4112 100644
--- a/BRYHTMLParser/HTMLNode.h
+++ b/BRYHTMLParser/HTMLNode.h
@@ -40,57 +40,57 @@ typedef NS_ENUM(unsigned int, HTMLNodeType) {
 @protocol HTMLNode <NSObject>
 
 /// Returns the first child element
-@property (nonatomic, readonly) id <HTMLNode> firstChild;
+@property (nonatomic, readonly, nullable) id <HTMLNode> firstChild;
 
 /// Returns the plaintext contents of node
-@property (nonatomic, readonly, copy) NSString *contents;
+@property (nonatomic, readonly, copy, nullable) NSString *contents;
 
 /// Returns the plaintext contents of this node + all children
-@property (nonatomic, readonly, copy) NSString *allContents;
+@property (nonatomic, readonly, copy, nullable) NSString *allContents;
 
 /// Returns the html contents of the node
-@property (nonatomic, readonly, copy) NSString *rawContents;
+@property (nonatomic, readonly, copy, nullable) NSString *rawContents;
 
 /// Returns next sibling in tree
-@property (nonatomic, readonly) id <HTMLNode> nextSibling;
+@property (nonatomic, readonly, nullable) id <HTMLNode> nextSibling;
 
 /// Returns previous sibling in tree
-@property (nonatomic, readonly) id <HTMLNode> previousSibling;
+@property (nonatomic, readonly, nullable) id <HTMLNode> previousSibling;
 
 /// Returns the class name
-@property (nonatomic, readonly, copy) NSString *className;
+@property (nonatomic, readonly, copy, nullable) NSString *className;
 
 /// Returns the tag name
-@property (nonatomic, readonly, copy) NSString *tagName;
+@property (nonatomic, readonly, copy, nullable) NSString *tagName;
 
 /// Returns the parent
-@property (nonatomic, readonly) id <HTMLNode> parent;
+@property (nonatomic, readonly, nullable) id <HTMLNode> parent;
 
 /// Returns the first level of children
-@property (nonatomic, readonly, copy) NSArray *children;
+@property (nonatomic, readonly, copy, nonnull) NSArray<id<HTMLNode>> *children;
 
 /// Returns the node type if know
 @property (nonatomic, readonly) HTMLNodeType nodetype;
 
 /// Gets the attribute value matching tha name
-- (NSString *)getAttributeNamed:(NSString *)name;
+- (nullable NSString *)getAttributeNamed:(nonnull NSString *)name;
 
 /// Find children with the specified tag name
-- (NSArray *)findChildTags:(NSString *)tagName;
+- (nonnull NSArray<id<HTMLNode>> *)findChildTags:(nonnull NSString *)tagName;
 
 /// Looks for a tag name e.g. "h3"
-- (id <HTMLNode>)findChildTag:(NSString *)tagName;
+- (nullable id <HTMLNode>)findChildTag:(nonnull NSString *)tagName;
 
 /// Returns a single child of class
-- (id <HTMLNode>)findChildOfClass:(NSString *)className;
+- (nullable id <HTMLNode>)findChildOfClass:(nonnull NSString *)className;
 
 /// Returns all children of class
-- (NSArray *)findChildrenOfClass:(NSString *)className;
+- (nonnull NSArray<id<HTMLNode>> *)findChildrenOfClass:(nonnull NSString *)className;
 
 /// Finds a single child with a matching attribute. Set `allowPartial` to match partial matches, e.g. <img src="http://www.google.com> [findChildWithAttribute:@"src" matchingName:"google.com" allowPartial:TRUE]
-- (id <HTMLNode>)findChildWithAttribute:(NSString *)attribute matchingName:(NSString *)className allowPartial:(BOOL)partial;
+- (nullable id <HTMLNode>)findChildWithAttribute:(nonnull NSString *)attribute matchingName:(nonnull NSString *)className allowPartial:(BOOL)partial;
 
 /// Finds all children with a matching attribute
-- (NSArray *)findChildrenWithAttribute:(NSString *)attribute matchingName:(NSString *)className allowPartial:(BOOL)partial;
+- (nonnull NSArray<id<HTMLNode>> *)findChildrenWithAttribute:(nonnull NSString *)attribute matchingName:(nonnull NSString *)className allowPartial:(BOOL)partial;
 
 @end
diff --git a/BRYHTMLParser/HTMLParser.h b/BRYHTMLParser/HTMLParser.h
index f8242d2..96bd89e 100644
--- a/BRYHTMLParser/HTMLParser.h
+++ b/BRYHTMLParser/HTMLParser.h
@@ -12,21 +12,21 @@
 @interface HTMLParser : NSObject
 
 /// Returns the doc tag
-@property (nonatomic, readonly) id <HTMLNode> doc;
+@property (nonatomic, readonly, nullable) id <HTMLNode> doc;
 
 /// Returns the body tag
-@property (nonatomic, readonly) id <HTMLNode> body;
+@property (nonatomic, readonly, nullable) id <HTMLNode> body;
 
 /// Returns the html tag
-@property (nonatomic, readonly) id <HTMLNode> html;
+@property (nonatomic, readonly, nullable) id <HTMLNode> html;
 
 /// Returns the head tag
-@property (nonatomic, readonly) id <HTMLNode> head;
+@property (nonatomic, readonly, nullable) id <HTMLNode> head;
 
-- (instancetype)initWithContentsOfURL:(NSURL *)url error:(NSError **)error;
+- (nullable instancetype)initWithContentsOfURL:(nonnull NSURL *)url error:(NSError * _Nullable * _Nullable)error;
 
-- (instancetype)initWithData:(NSData *)data error:(NSError **)error NS_DESIGNATED_INITIALIZER;
+- (nonnull instancetype)initWithData:(nonnull NSData *)data error:(NSError * _Nullable * _Nullable)error NS_DESIGNATED_INITIALIZER;
 
-- (instancetype)initWithString:(NSString *)string error:(NSError **)error NS_DESIGNATED_INITIALIZER;
+- (nonnull instancetype)initWithString:(nonnull NSString *)string error:(NSError * _Nullable * _Nullable)error NS_DESIGNATED_INITIALIZER;
 
 @end
diff --git a/BRYHTMLParser/LibXMLHTMLNode.h b/BRYHTMLParser/LibXMLHTMLNode.h
index 9c90cd6..ac27def 100644
--- a/BRYHTMLParser/LibXMLHTMLNode.h
+++ b/BRYHTMLParser/LibXMLHTMLNode.h
@@ -14,6 +14,6 @@
 struct _xmlNode;
 
 /// Init with a lib xml node (shouldn't need to be called manually). Use [parser doc] to get the root Node
-- (instancetype)initWithXMLNode:(struct _xmlNode *)xmlNode NS_DESIGNATED_INITIALIZER;
+- (nonnull instancetype)initWithXMLNode:(struct _xmlNode * _Nullable)xmlNode NS_DESIGNATED_INITIALIZER;
 
 @end