diff --git a/HTMLKit/HTMLOrderedDictionary.h b/HTMLKit/HTMLOrderedDictionary.h
index aad6baf..088b02a 100644
--- a/HTMLKit/HTMLOrderedDictionary.h
+++ b/HTMLKit/HTMLOrderedDictionary.h
@@ -8,18 +8,22 @@
 
 #import <Foundation/Foundation.h>
 
-@interface HTMLOrderedDictionary : NSMutableDictionary
+NS_ASSUME_NONNULL_BEGIN
 
-- (id)objectAtIndex:(NSUInteger)index;
-- (void)setObject:(id)anObject forKey:(id<NSCopying>)aKey atIndex:(NSUInteger)index;
+@interface HTMLOrderedDictionary<KeyType, ObjectType> : NSMutableDictionary<KeyType, ObjectType>
+
+- (ObjectType)objectAtIndex:(NSUInteger)index;
+- (void)setObject:(ObjectType)anObject forKey:(KeyType<NSCopying>)aKey atIndex:(NSUInteger)index;
 - (void)removeObjectAtIndex:(NSUInteger)index;
-- (void)replaceKeyValueAtIndex:(NSUInteger)index withObject:(id)anObject andKey:(id<NSCopying>)aKey;
-- (void)replaceKey:(id<NSCopying>)aKey withKey:(id<NSCopying>)newKey;
-- (NSUInteger)indexOfKey:(id<NSCopying>)aKey;
+- (void)replaceKeyValueAtIndex:(NSUInteger)index withObject:(ObjectType)anObject andKey:(KeyType<NSCopying>)aKey;
+- (void)replaceKey:(KeyType<NSCopying>)aKey withKey:(KeyType<NSCopying>)newKey;
+- (NSUInteger)indexOfKey:(KeyType<NSCopying>)aKey;
 
-- (id)objectAtIndexedSubscript:(NSUInteger)index;
-- (void)setObject:(id)obj atIndexedSubscript:(NSUInteger)index;
+- (ObjectType)objectAtIndexedSubscript:(NSUInteger)index;
+- (void)setObject:(ObjectType)obj atIndexedSubscript:(NSUInteger)index;
 
 - (NSEnumerator *)reverseKeyEnumerator;
 
 @end
+
+NS_ASSUME_NONNULL_END
diff --git a/HTMLKitTests/HTMLKitOrderedDictionaryTests.m b/HTMLKitTests/HTMLKitOrderedDictionaryTests.m
index c9bf8c1..d58c6cf 100644
--- a/HTMLKitTests/HTMLKitOrderedDictionaryTests.m
+++ b/HTMLKitTests/HTMLKitOrderedDictionaryTests.m
@@ -38,9 +38,6 @@
 	[_dictionary setObject:@"3" forKey:@"C"];
 	expected =  @[@"A", @"B", @"C"];
 	XCTAssertEqualObjects(_dictionary.keyEnumerator.allObjects, expected);
-
-	XCTAssertThrows([_dictionary setObject:nil forKey:@"Key"]);
-	XCTAssertThrows([_dictionary setObject:@"Object" forKey:nil]);
 }
 
 - (void)testIndexOfKey
@@ -51,7 +48,6 @@
 	XCTAssertEqual([_dictionary indexOfKey:@"A"], 0);
 	XCTAssertEqual([_dictionary indexOfKey:@"B"], 1);
 	XCTAssertEqual([_dictionary indexOfKey:@"C"], 2);
-	XCTAssertEqual([_dictionary indexOfKey:nil], NSNotFound);
 }
 
 - (void)testObjectAtIndex
@@ -64,8 +60,6 @@
 	[_dictionary setObject:@"3" forKey:@"C" atIndex:1];
 	XCTAssertEqualObjects([_dictionary objectAtIndex:1], @"3");
 
-	XCTAssertThrows([_dictionary setObject:nil forKey:@"Key" atIndex:0]);
-	XCTAssertThrows([_dictionary setObject:@"Object" forKey:nil atIndex:0]);
 	XCTAssertThrows([_dictionary setObject:@"Object" forKey:@"Key" atIndex:100]);
 }
 
@@ -120,8 +114,6 @@
 	XCTAssertEqualObjects(_dictionary[2], @"5");
 	XCTAssertEqualObjects(_dictionary[@"A"], @"5");
 
-	XCTAssertThrows([_dictionary setObject:nil forKey:@"Key" atIndex:0]);
-	XCTAssertThrows([_dictionary setObject:@"Object" forKey:nil atIndex:0]);
 	XCTAssertThrows([_dictionary setObject:@"Object" forKey:@"Key" atIndex:100]);
 }
 
@@ -158,8 +150,6 @@
 	XCTAssertEqualObjects(_dictionary[0], @"5");
 	XCTAssertEqualObjects(_dictionary[@"E"], @"5");
 
-	XCTAssertThrows([_dictionary replaceKeyValueAtIndex:1 withObject:nil andKey:@"Key"]);
-	XCTAssertThrows([_dictionary replaceKeyValueAtIndex:1 withObject:@"Object" andKey:nil]);
 	XCTAssertThrows([_dictionary replaceKeyValueAtIndex:100 withObject:@"Object" andKey:@"Key"]);
 }