Index: src/OFArray.m
==================================================================
--- src/OFArray.m
+++ src/OFArray.m
@@ -185,19 +185,19 @@
 - (instancetype)initWithObject: (id)firstObject arguments: (va_list)arguments
 {
 	size_t count = 1;
 	va_list argumentsCopy;
 	id *objects;
+
+	if (firstObject == nil)
+		return [self init];
 
 	va_copy(argumentsCopy, arguments);
 	while (va_arg(argumentsCopy, id) != nil)
 		count++;
 
 	@try {
-		if (firstObject == nil)
-			@throw [OFInvalidArgumentException exception];
-
 		objects = OFAllocMemory(count, sizeof(id));
 	} @catch (id e) {
 		[self release];
 		@throw e;
 	}

Index: src/OFCountedSet.m
==================================================================
--- src/OFCountedSet.m
+++ src/OFCountedSet.m
@@ -28,10 +28,16 @@
 
 @interface OFPlaceholderCountedSet: OFCountedSet
 @end
 
 @implementation OFPlaceholderCountedSet
+#ifdef __clang__
+/* We intentionally don't call into super, so silence the warning. */
+# pragma clang diagnostic push
+# pragma clang diagnostic ignored "-Wunknown-pragmas"
+# pragma clang diagnostic ignored "-Wobjc-designated-initializers"
+#endif
 - (instancetype)init
 {
 	return (id)[[OFConcreteCountedSet alloc] init];
 }
 
@@ -67,10 +73,13 @@
 - (instancetype)initWithObject: (id)firstObject arguments: (va_list)arguments
 {
 	return (id)[[OFConcreteCountedSet alloc] initWithObject: firstObject
 						      arguments: arguments];
 }
+#ifdef __clang__
+# pragma clang diagnostic pop
+#endif
 
 OF_SINGLETON_METHODS
 @end
 
 @implementation OFCountedSet

Index: src/OFDictionary.m
==================================================================
--- src/OFDictionary.m
+++ src/OFDictionary.m
@@ -256,17 +256,15 @@
 	} @catch (id e) {
 		[self release];
 		@throw e;
 	}
 
-	@try {
-		return [self initWithObjects: objects
-				     forKeys: keys
-				       count: count];
-	} @finally {
-		objc_autoreleasePoolPop(pool);
-	}
+	self = [self initWithObjects: objects forKeys: keys count: count];
+
+	objc_autoreleasePoolPop(pool);
+
+	return self;
 }
 
 #ifdef __clang__
 /* We intentionally don't call into super, so silence the warning. */
 # pragma clang diagnostic push
@@ -298,20 +296,23 @@
 - (instancetype)initWithKey: (id)firstKey arguments: (va_list)arguments
 {
 	size_t count = 1;
 	id *objects = NULL, *keys = NULL;
 	va_list argumentsCopy;
+
+	if (firstKey == nil)
+		return [self init];
 
 	va_copy(argumentsCopy, arguments);
 	while (va_arg(argumentsCopy, id) != nil)
 		count++;
 
 	@try {
 		size_t i = 0;
 		id key, object;
 
-		if (firstKey == nil || count % 2 != 0)
+		if (count % 2 != 0)
 			@throw [OFInvalidArgumentException exception];
 
 		count /= 2;
 
 		objects = OFAllocMemory(count, sizeof(id));

Index: src/OFMutableSet.h
==================================================================
--- src/OFMutableSet.h
+++ src/OFMutableSet.h
@@ -36,18 +36,25 @@
  * @param capacity The initial capacity for the OFMutableSet
  * @return A new autoreleased OFMutableSet
  */
 + (instancetype)setWithCapacity: (size_t)capacity;
 
+/**
+ * @brief Initializes an already allocated OFMutableSet to be empty.
+ *
+ * @return An initialized OFMutableSet
+ */
+- (instancetype)init OF_DESIGNATED_INITIALIZER;
+
 /**
  * @brief Initializes an already allocated OFMutableSet with enough memory to
  *	  hold the specified number of objects.
  *
  * @param capacity The initial capacity for the OFMutableSet
  * @return An initialized OFMutableSet
  */
-- (instancetype)initWithCapacity: (size_t)capacity;
+- (instancetype)initWithCapacity: (size_t)capacity OF_DESIGNATED_INITIALIZER;
 
 /**
  * @brief Adds the specified object to the set.
  *
  * @param object The object to add to the set

Index: src/OFMutableSet.m
==================================================================
--- src/OFMutableSet.m
+++ src/OFMutableSet.m
@@ -27,10 +27,16 @@
 
 @interface OFPlaceholderMutableSet: OFMutableSet
 @end
 
 @implementation OFPlaceholderMutableSet
+#ifdef __clang__
+/* We intentionally don't call into super, so silence the warning. */
+# pragma clang diagnostic push
+# pragma clang diagnostic ignored "-Wunknown-pragmas"
+# pragma clang diagnostic ignored "-Wobjc-designated-initializers"
+#endif
 - (instancetype)init
 {
 	return (id)[[OFConcreteMutableSet alloc] init];
 }
 
@@ -71,10 +77,13 @@
 
 - (instancetype)initWithCapacity: (size_t)capacity
 {
 	return (id)[[OFConcreteMutableSet alloc] initWithCapacity: capacity];
 }
+#ifdef __clang__
+# pragma clang diagnostic pop
+#endif
 
 OF_SINGLETON_METHODS
 @end
 
 @implementation OFMutableSet
@@ -95,15 +104,34 @@
 
 + (instancetype)setWithCapacity: (size_t)capacity
 {
 	return [[[self alloc] initWithCapacity: capacity] autorelease];
 }
+
+- (instancetype)init
+{
+	return [super init];
+}
+
+#ifdef __clang__
+/* We intentionally don't call into super, so silence the warning. */
+# pragma clang diagnostic push
+# pragma clang diagnostic ignored "-Wunknown-pragmas"
+# pragma clang diagnostic ignored "-Wobjc-designated-initializers"
+#endif
+- (instancetype)initWithObjects: (id const *)objects count: (size_t)count
+{
+	OF_INVALID_INIT_METHOD
+}
 
 - (instancetype)initWithCapacity: (size_t)capacity
 {
 	OF_INVALID_INIT_METHOD
 }
+#ifdef __clang__
+# pragma clang diagnostic pop
+#endif
 
 - (id)copy
 {
 	return [[OFSet alloc] initWithSet: self];
 }

Index: src/OFSet.h
==================================================================
--- src/OFSet.h
+++ src/OFSet.h
@@ -115,10 +115,17 @@
  * @return A new, autoreleased set with the specified objects
  */
 + (instancetype)setWithObjects: (ObjectType const _Nonnull *_Nonnull)objects
 			 count: (size_t)count;
 
+/**
+ * @brief Initializes an already allocated set to be empty.
+ *
+ * @return An initialized set
+ */
+- (instancetype)init OF_DESIGNATED_INITIALIZER;
+
 /**
  * @brief Initializes an already allocated set with the specified set.
  *
  * @param set The set to initialize the set with
  * @return An initialized set with the specified set
@@ -158,11 +165,11 @@
  * @param objects An array of objects for the set
  * @param count The number of objects in the specified array
  * @return An initialized set with the specified objects
  */
 - (instancetype)initWithObjects: (ObjectType const _Nonnull *_Nonnull)objects
-			  count: (size_t)count;
+			  count: (size_t)count OF_DESIGNATED_INITIALIZER;
 
 /**
  * @brief Returns an OFEnumerator to enumerate through all objects of the set.
  *
  * @return An OFEnumerator to enumerate through all objects of the set

Index: src/OFSet.m
==================================================================
--- src/OFSet.m
+++ src/OFSet.m
@@ -30,10 +30,16 @@
 
 @interface OFPlaceholderSet: OFSet
 @end
 
 @implementation OFPlaceholderSet
+#ifdef __clang__
+/* We intentionally don't call into super, so silence the warning. */
+# pragma clang diagnostic push
+# pragma clang diagnostic ignored "-Wunknown-pragmas"
+# pragma clang diagnostic ignored "-Wobjc-designated-initializers"
+#endif
 - (instancetype)init
 {
 	return (id)[[OFConcreteSet alloc] init];
 }
 
@@ -69,10 +75,13 @@
 - (instancetype)initWithObject: (id)firstObject arguments: (va_list)arguments
 {
 	return (id)[[OFConcreteSet alloc] initWithObject: firstObject
 					       arguments: arguments];
 }
+#ifdef __clang__
+# pragma clang diagnostic pop
+#endif
 
 OF_SINGLETON_METHODS
 @end
 
 @implementation OFSet
@@ -142,22 +151,74 @@
 	return [super init];
 }
 
 - (instancetype)initWithSet: (OFSet *)set
 {
-	OF_INVALID_INIT_METHOD
+	id *objects = NULL;
+	size_t count;
+
+	@try {
+		void *pool = objc_autoreleasePoolPush();
+		size_t i = 0;
+
+		count = set.count;
+		objects = OFAllocMemory(count, sizeof(id));
+
+		for (id object in set) {
+			OFEnsure(i < count);
+			objects[i++] = object;
+		}
+
+		objc_autoreleasePoolPop(pool);
+	} @catch (id e) {
+		OFFreeMemory(objects);
+
+		[self release];
+		@throw e;
+	}
+
+	@try {
+		return [self initWithObjects: objects count: count];
+	} @finally {
+		OFFreeMemory(objects);
+	}
 }
 
 - (instancetype)initWithArray: (OFArray *)array
 {
-	OF_INVALID_INIT_METHOD
+	void *pool = objc_autoreleasePoolPush();
+	size_t count;
+	const id *objects;
+
+	@try {
+		count = array.count;
+		objects = array.objects;
+	} @catch (id e) {
+		[self release];
+		@throw e;
+	}
+
+	self = [self initWithObjects: objects count: count];
+
+	objc_autoreleasePoolPop(pool);
+
+	return self;
 }
 
+#ifdef __clang__
+/* We intentionally don't call into super, so silence the warning. */
+# pragma clang diagnostic push
+# pragma clang diagnostic ignored "-Wunknown-pragmas"
+# pragma clang diagnostic ignored "-Wobjc-designated-initializers"
+#endif
 - (instancetype)initWithObjects: (id const *)objects count: (size_t)count
 {
 	OF_INVALID_INIT_METHOD
 }
+#ifdef __clang__
+# pragma clang diagnostic pop
+#endif
 
 - (instancetype)initWithObjects: (id)firstObject, ...
 {
 	id ret;
 	va_list arguments;
@@ -169,11 +230,40 @@
 	return ret;
 }
 
 - (instancetype)initWithObject: (id)firstObject arguments: (va_list)arguments
 {
-	OF_INVALID_INIT_METHOD
+	size_t count = 1;
+	va_list argumentsCopy;
+	id *objects;
+
+	if (firstObject == nil)
+		return [self init];
+
+	va_copy(argumentsCopy, arguments);
+	while (va_arg(argumentsCopy, id) != nil)
+		count++;
+
+	@try {
+		objects = OFAllocMemory(count, sizeof(id));
+	} @catch (id e) {
+		[self release];
+		@throw e;
+	}
+
+	@try {
+		objects[0] = firstObject;
+
+		for (size_t i = 1; i < count; i++) {
+			objects[i] = va_arg(arguments, id);
+			OFEnsure(objects[i] != nil);
+		}
+
+		return [self initWithObjects: objects count: count];
+	} @finally {
+		OFFreeMemory(objects);
+	}
 }
 
 - (size_t)count
 {
 	OF_UNRECOGNIZED_SELECTOR