diff --git a/Parse.xcodeproj/project.pbxproj b/Parse.xcodeproj/project.pbxproj
index d8df3f0a9..d8684a59b 100644
--- a/Parse.xcodeproj/project.pbxproj
+++ b/Parse.xcodeproj/project.pbxproj
@@ -8597,6 +8597,7 @@
 			isa = XCBuildConfiguration;
 			baseConfigurationReference = 81DCD1491D2DA080002501A2 /* Debug.xcconfig */;
 			buildSettings = {
+				SWIFT_VERSION = 3.0;
 			};
 			name = Debug;
 		};
@@ -8604,6 +8605,7 @@
 			isa = XCBuildConfiguration;
 			baseConfigurationReference = 81DCD14A1D2DA080002501A2 /* Release.xcconfig */;
 			buildSettings = {
+				SWIFT_VERSION = 3.0;
 			};
 			name = Release;
 		};
diff --git a/Parse/Internal/ACL/State/PFACLState.h b/Parse/Internal/ACL/State/PFACLState.h
index d0c6c439b..4a1d30761 100644
--- a/Parse/Internal/ACL/State/PFACLState.h
+++ b/Parse/Internal/ACL/State/PFACLState.h
@@ -17,7 +17,7 @@ typedef void (^PFACLStateMutationBlock)(PFMutableACLState *);
 
 @interface PFACLState : PFBaseState<PFBaseStateSubclass, NSCopying, NSMutableCopying>
 
-@property (nonatomic, copy, readonly) NSDictionary<NSString *, id> *permissions;
+@property (nonatomic, strong, readonly) NSDictionary<NSString *, id> *permissions;
 @property (nonatomic, assign, readonly, getter=isShared) BOOL shared;
 
 ///--------------------------------------
diff --git a/Parse/Internal/ACL/State/PFACLState_Private.h b/Parse/Internal/ACL/State/PFACLState_Private.h
index bab64a182..e2906f410 100644
--- a/Parse/Internal/ACL/State/PFACLState_Private.h
+++ b/Parse/Internal/ACL/State/PFACLState_Private.h
@@ -26,7 +26,7 @@
     BOOL _shared;
 }
 
-@property (nonatomic, copy, readwrite) NSDictionary<NSString *, id> *permissions;
+@property (nonatomic, strong, readwrite) NSDictionary<NSString *, id> *permissions;
 @property (nonatomic, assign, readwrite, getter=isShared) BOOL shared;
 
 @end
diff --git a/Parse/Internal/ACL/State/PFMutableACLState.h b/Parse/Internal/ACL/State/PFMutableACLState.h
index f0a1a1c41..229e1465c 100644
--- a/Parse/Internal/ACL/State/PFMutableACLState.h
+++ b/Parse/Internal/ACL/State/PFMutableACLState.h
@@ -13,7 +13,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface PFMutableACLState : PFACLState
 
-@property (nonatomic, copy, readwrite) NSMutableDictionary<NSString *, id> *permissions;
+@property (nonatomic, strong, readwrite) NSMutableDictionary<NSString *, id> *permissions;
 @property (nonatomic, assign, readwrite, getter=isShared) BOOL shared;
 
 @end
diff --git a/Parse/Internal/KeyValueCache/PFKeyValueCache.h b/Parse/Internal/KeyValueCache/PFKeyValueCache.h
index 5faef2bc9..7768d13f9 100644
--- a/Parse/Internal/KeyValueCache/PFKeyValueCache.h
+++ b/Parse/Internal/KeyValueCache/PFKeyValueCache.h
@@ -35,7 +35,7 @@ NS_ASSUME_NONNULL_BEGIN
 #pragma mark - Getting
 ///--------------------------------------
 
-- (NSString *)objectForKey:(NSString *)key maxAge:(NSTimeInterval)age;
+- (nullable NSString *)objectForKey:(NSString *)key maxAge:(NSTimeInterval)age;
 
 ///--------------------------------------
 #pragma mark - Removing
diff --git a/Parse/Internal/KeyValueCache/PFKeyValueCache.m b/Parse/Internal/KeyValueCache/PFKeyValueCache.m
index 77c755ebd..b75cd6492 100644
--- a/Parse/Internal/KeyValueCache/PFKeyValueCache.m
+++ b/Parse/Internal/KeyValueCache/PFKeyValueCache.m
@@ -127,7 +127,7 @@ - (void)setObject:(NSString *)value forKey:(NSString *)key {
     });
 }
 
-- (NSString *)objectForKey:(NSString *)key maxAge:(NSTimeInterval)maxAge {
+- (nullable NSString *)objectForKey:(NSString *)key maxAge:(NSTimeInterval)maxAge {
     NSURL *cacheURL = [self _cacheURLForKey:key];
     PFKeyValueCacheEntry *cacheEntry = [self.memoryCache objectForKey:key];
 
diff --git a/Parse/Internal/LocalDataStore/OfflineQueryLogic/PFOfflineQueryLogic.m b/Parse/Internal/LocalDataStore/OfflineQueryLogic/PFOfflineQueryLogic.m
index 3ff4530d0..9eddc757c 100644
--- a/Parse/Internal/LocalDataStore/OfflineQueryLogic/PFOfflineQueryLogic.m
+++ b/Parse/Internal/LocalDataStore/OfflineQueryLogic/PFOfflineQueryLogic.m
@@ -145,7 +145,7 @@ - (id)valueForContainer:(id)container
         } else if ([key isEqualToString:@"updatedAt"] || [key isEqualToString:@"_updated_at"]) {
             return object.updatedAt;
         } else {
-            return object[key];
+            return key ? object[key] : nil;
         }
     } else if ([container isKindOfClass:[NSDictionary class]]) {
         return ((NSDictionary *)container)[key];
diff --git a/Parse/Internal/Object/PFObjectPrivate.h b/Parse/Internal/Object/PFObjectPrivate.h
index 5ce305ff2..fb8714e76 100644
--- a/Parse/Internal/Object/PFObjectPrivate.h
+++ b/Parse/Internal/Object/PFObjectPrivate.h
@@ -85,7 +85,7 @@
  @return Current object state.
  */
 @property (nonatomic, copy) PFObjectState *_state;
-@property (nonatomic, copy) NSMutableSet *_availableKeys;
+@property (nonatomic, strong) NSMutableSet *_availableKeys;
 
 - (instancetype)initWithObjectState:(PFObjectState *)state;
 + (instancetype)objectWithClassName:(NSString *)className
diff --git a/Parse/Internal/Object/Subclassing/PFObjectSubclassingController.m b/Parse/Internal/Object/Subclassing/PFObjectSubclassingController.m
index 1be108765..e5c8e1a36 100644
--- a/Parse/Internal/Object/Subclassing/PFObjectSubclassingController.m
+++ b/Parse/Internal/Object/Subclassing/PFObjectSubclassingController.m
@@ -343,7 +343,12 @@ - (void)_registerSubclassesInLoadedBundle:(NSBundle *)bundle {
 }
 
 - (void)_registerSubclassesInBundle:(NSBundle *)bundle {
-    PFConsistencyAssert(bundle.loaded, @"Cannot register subclasses in an unloaded bundle: %@", bundle);
+    // Prevent crash by loading the bundle if it's not loaded yet (see: https://github.com/ParsePlatform/Parse-SDK-iOS-OSX/issues/1006 ):
+    NSError *error = nil;
+    if (!bundle.loaded) {
+        [bundle loadAndReturnError:&error];
+    }
+    PFConsistencyAssert(bundle.loaded, @"Cannot register subclasses in a bundle that hasn't been loaded!");
 
     const char *executablePath = bundle.executablePath.UTF8String;
     if (executablePath == NULL) {
diff --git a/Parse/Internal/Object/Utilities/PFObjectUtilities.h b/Parse/Internal/Object/Utilities/PFObjectUtilities.h
index f4b225141..8044d1dab 100644
--- a/Parse/Internal/Object/Utilities/PFObjectUtilities.h
+++ b/Parse/Internal/Object/Utilities/PFObjectUtilities.h
@@ -20,7 +20,7 @@ NS_ASSUME_NONNULL_BEGIN
 #pragma mark - Operations
 ///--------------------------------------
 
-+ (id)newValueByApplyingFieldOperation:(PFFieldOperation *)operation
++ (nullable id)newValueByApplyingFieldOperation:(PFFieldOperation *)operation
                           toDictionary:(NSMutableDictionary *)dictionary
                                 forKey:(NSString *)key;
 + (void)applyOperationSet:(PFOperationSet *)operationSet toDictionary:(NSMutableDictionary *)dictionary;
diff --git a/Parse/Internal/Object/Utilities/PFObjectUtilities.m b/Parse/Internal/Object/Utilities/PFObjectUtilities.m
index 9b5f1e12b..58e5fb80e 100644
--- a/Parse/Internal/Object/Utilities/PFObjectUtilities.m
+++ b/Parse/Internal/Object/Utilities/PFObjectUtilities.m
@@ -18,7 +18,7 @@ @implementation PFObjectUtilities
 #pragma mark - Operations
 ///--------------------------------------
 
-+ (id)newValueByApplyingFieldOperation:(PFFieldOperation *)operation
++ (nullable id)newValueByApplyingFieldOperation:(PFFieldOperation *)operation
                           toDictionary:(NSMutableDictionary *)dictionary
                                 forKey:(NSString *)key {
     id oldValue = dictionary[key];
diff --git a/Parse/Internal/PFDateFormatter.h b/Parse/Internal/PFDateFormatter.h
index 3fb91092b..ff92b55be 100644
--- a/Parse/Internal/PFDateFormatter.h
+++ b/Parse/Internal/PFDateFormatter.h
@@ -26,7 +26,7 @@ NS_ASSUME_NONNULL_BEGIN
 
  @return Formatted `NSString` representation.
  */
-- (NSString *)preciseStringFromDate:(NSDate *)date;
+- (nullable NSString *)preciseStringFromDate:(NSDate *)date;
 
 ///--------------------------------------
 #pragma mark - Date from String
diff --git a/Parse/Internal/PFDateFormatter.m b/Parse/Internal/PFDateFormatter.m
index 1f8707929..78d47ea53 100644
--- a/Parse/Internal/PFDateFormatter.m
+++ b/Parse/Internal/PFDateFormatter.m
@@ -69,7 +69,7 @@ - (void)dealloc {
 #pragma mark - String from Date
 ///--------------------------------------
 
-- (NSString *)preciseStringFromDate:(NSDate *)date {
+- (nullable NSString *)preciseStringFromDate:(NSDate *)date {
     __block NSString *string = nil;
     NSTimeInterval interval = date.timeIntervalSince1970;
     dispatch_sync(_synchronizationQueue, ^{
diff --git a/Parse/Internal/PFEventuallyQueue.m b/Parse/Internal/PFEventuallyQueue.m
index 663024e7b..0de7782da 100644
--- a/Parse/Internal/PFEventuallyQueue.m
+++ b/Parse/Internal/PFEventuallyQueue.m
@@ -73,7 +73,9 @@ - (instancetype)initWithDataSource:(id<PFCommandRunnerProvider>)dataSource
     _commandEnqueueTaskQueue = [[PFTaskQueue alloc] init];
 
     _taskCompletionSources = [NSMutableDictionary dictionary];
-    _testHelper = [[PFEventuallyQueueTestHelper alloc] init];
+    
+    // we don't want your leaky test helper
+//    _testHelper = [[PFEventuallyQueueTestHelper alloc] init];
 
     [self _startMonitoringNetworkReachability];
 
diff --git a/Parse/Internal/PropertyInfo/PFPropertyInfo.m b/Parse/Internal/PropertyInfo/PFPropertyInfo.m
index d3c856e95..f875dd606 100644
--- a/Parse/Internal/PropertyInfo/PFPropertyInfo.m
+++ b/Parse/Internal/PropertyInfo/PFPropertyInfo.m
@@ -58,7 +58,7 @@ - (instancetype)initWithClass:(Class)kls name:(NSString *)propertyName
         _ivar = class_getInstanceVariable(kls, safeStringWithPropertyAttributeValue(objcProperty, "V").UTF8String);
         if (_ivar) break;
 
-        // Walk the superclass heirarchy for the property definition. Because property attributes are not inherited
+        // Walk the superclass hierarchy for the property definition. Because property attributes are not inherited
         // (but property definitions *are*), we must be careful to ensure that the variable was never actually
         // implemented and synthesized in a superclass. Note if the same property is synthesized in multiple classes
         // with different iVars, we take the class furthest from the root class as the 'source of truth'.
@@ -94,7 +94,9 @@ - (instancetype)initWithClass:(Class)kls name:(NSString *)propertyName
         propertySetter = [NSString stringWithFormat:@"set%@:", stringByCapitalizingFirstCharacter(_name)];
     }
 
-    _setterSelector = NSSelectorFromString(propertySetter);
+    if (propertySetter != nil) {
+        _setterSelector = NSSelectorFromString(propertySetter);
+    }
 
     if (_associationType == PFPropertyInfoAssociationTypeDefault) {
         BOOL isCopy = safeStringWithPropertyAttributeValue(objcProperty, "C") != nil;
diff --git a/Parse/Internal/Query/Controller/PFQueryController.h b/Parse/Internal/Query/Controller/PFQueryController.h
index adf809457..16637df04 100644
--- a/Parse/Internal/Query/Controller/PFQueryController.h
+++ b/Parse/Internal/Query/Controller/PFQueryController.h
@@ -78,7 +78,7 @@ NS_ASSUME_NONNULL_BEGIN
 #pragma mark - Caching
 ///--------------------------------------
 
-- (NSString *)cacheKeyForQueryState:(PFQueryState *)queryState sessionToken:(nullable NSString *)sessionToken;
+- (nullable NSString *)cacheKeyForQueryState:(PFQueryState *)queryState sessionToken:(nullable NSString *)sessionToken;
 - (BOOL)hasCachedResultForQueryState:(PFQueryState *)queryState sessionToken:(nullable NSString *)sessionToken;
 
 - (void)clearCachedResultForQueryState:(PFQueryState *)queryState sessionToken:(nullable NSString *)sessionToken;
diff --git a/Parse/Internal/Query/Controller/PFQueryController.m b/Parse/Internal/Query/Controller/PFQueryController.m
index 9058ab305..667ac7583 100644
--- a/Parse/Internal/Query/Controller/PFQueryController.m
+++ b/Parse/Internal/Query/Controller/PFQueryController.m
@@ -127,7 +127,7 @@ - (BFTask *)countObjectsAsyncForQueryState:(PFQueryState *)queryState
 #pragma mark - Caching
 ///--------------------------------------
 
-- (NSString *)cacheKeyForQueryState:(PFQueryState *)queryState sessionToken:(NSString *)sessionToken {
+- (nullable NSString *)cacheKeyForQueryState:(PFQueryState *)queryState sessionToken:(NSString *)sessionToken {
     return nil;
 }
 
diff --git a/Parse/Internal/Relation/State/PFMutableRelationState.h b/Parse/Internal/Relation/State/PFMutableRelationState.h
index 3fd99eddb..67174ad02 100644
--- a/Parse/Internal/Relation/State/PFMutableRelationState.h
+++ b/Parse/Internal/Relation/State/PFMutableRelationState.h
@@ -13,7 +13,7 @@
 
 @property (nonatomic, weak, readwrite) PFObject *parent;
 @property (nonatomic, copy, readwrite) NSString *targetClass;
-@property (nonatomic, copy, readwrite) NSMutableSet *knownObjects;
+@property (nonatomic, strong, readwrite) NSMutableSet *knownObjects;
 @property (nonatomic, copy, readwrite) NSString *key;
 
 @end
diff --git a/Parse/Internal/Relation/State/PFRelationState.h b/Parse/Internal/Relation/State/PFRelationState.h
index 3ce8e80c0..48ad19642 100644
--- a/Parse/Internal/Relation/State/PFRelationState.h
+++ b/Parse/Internal/Relation/State/PFRelationState.h
@@ -17,7 +17,7 @@
 @property (nonatomic, copy, readonly) NSString *parentClassName;
 @property (nonatomic, copy, readonly) NSString *parentObjectId;
 @property (nonatomic, copy, readonly) NSString *targetClass;
-@property (nonatomic, copy, readonly) NSSet *knownObjects;
+@property (nonatomic, strong, readonly) NSSet *knownObjects;
 @property (nonatomic, copy, readonly) NSString *key;
 
 ///--------------------------------------
diff --git a/Parse/Internal/Relation/State/PFRelationState_Private.h b/Parse/Internal/Relation/State/PFRelationState_Private.h
index f8c841537..47efdd9ff 100644
--- a/Parse/Internal/Relation/State/PFRelationState_Private.h
+++ b/Parse/Internal/Relation/State/PFRelationState_Private.h
@@ -33,7 +33,7 @@
 @property (nonatomic, copy, readwrite) NSString *parentClassName;
 @property (nonatomic, copy, readwrite) NSString *parentObjectId;
 @property (nonatomic, copy, readwrite) NSString *targetClass;
-@property (nonatomic, copy, readwrite) NSSet *knownObjects;
+@property (nonatomic, strong, readwrite) NSSet *knownObjects;
 @property (nonatomic, copy, readwrite) NSString *key;
 
 @end
diff --git a/Parse/PFObject.m b/Parse/PFObject.m
index 21848f6c3..77ea51d27 100644
--- a/Parse/PFObject.m
+++ b/Parse/PFObject.m
@@ -776,7 +776,9 @@ + (id)_objectFromDictionary:(NSDictionary *)dictionary
                                    defaultClassName:defaultClassName
                                        completeData:(selectedKeys == nil)
                                             decoder:[PFDecoder objectDecoder]];
-    [result->_availableKeys addObjectsFromArray:selectedKeys];
+    if (selectedKeys) {
+        [result->_availableKeys addObjectsFromArray:selectedKeys];
+    }
     return result;
 }
 
@@ -789,7 +791,7 @@ + (id)_objectFromDictionary:(NSDictionary *)dictionary
  @param decoder Decoder used to decode the dictionary.
  */
 + (id)_objectFromDictionary:(NSDictionary *)dictionary
-           defaultClassName:(NSString *)defaultClassName
+           defaultClassName:(nonnull NSString *)defaultClassName
                completeData:(BOOL)completeData
                     decoder:(PFDecoder *)decoder {
     NSString *objectId = nil;
@@ -798,7 +800,8 @@ + (id)_objectFromDictionary:(NSDictionary *)dictionary
         objectId = dictionary[@"objectId"];
         className = dictionary[@"className"] ?: defaultClassName;
     }
-    PFObject *object = [PFObject objectWithoutDataWithClassName:className objectId:objectId];
+    // Temp fix for nil className possibility:
+    PFObject *object = [PFObject objectWithoutDataWithClassName:className ?: @"" objectId:objectId];
     [object _mergeAfterFetchWithResult:dictionary decoder:decoder completeData:completeData];
     return object;
 }
@@ -964,7 +967,7 @@ - (void)mergeFromRESTDictionary:(NSDictionary *)object withDecoder:(PFDecoder *)
                 }
 
                 PFOperationSet *localOperationSet = [self unsavedChanges];
-                if (localOperationSet.updatedAt != nil &&
+                if (localOperationSet.updatedAt != nil && remoteOperationSet.updatedAt != nil &&
                     [localOperationSet.updatedAt compare:remoteOperationSet.updatedAt] != NSOrderedAscending) {
                     [localOperationSet mergeOperationSet:remoteOperationSet];
                 } else {
@@ -1304,7 +1307,9 @@ - (void)_mergeFromServerWithResult:(NSDictionary *)result decoder:(PFDecoder *)d
                 state.updatedAt = state.createdAt;
             }
         }];
-        [_availableKeys addObjectsFromArray:result.allKeys];
+        if (result.allKeys) {
+            [_availableKeys addObjectsFromArray:result.allKeys];
+        }
 
         dirty = NO;
     }
diff --git a/Tests/Other/Swift/SwiftSubclass.swift b/Tests/Other/Swift/SwiftSubclass.swift
index 6db82970c..c83e5489e 100644
--- a/Tests/Other/Swift/SwiftSubclass.swift
+++ b/Tests/Other/Swift/SwiftSubclass.swift
@@ -16,7 +16,7 @@ public class SwiftSubclass: PFObject, PFSubclassing {
     @NSManaged public var primitiveProperty: Int
     @NSManaged public var objectProperty: AnyObject?
 
-    @NSManaged public var relationProperty: PFRelation?
+    @NSManaged public var relationProperty: PFRelation<PFObject>?
     @NSManaged public var badProperty: CGPoint
 
     public static func parseClassName() -> String {
diff --git a/Tests/Unit/ObjectSubclassingControllerTests.m b/Tests/Unit/ObjectSubclassingControllerTests.m
index 9e4306251..5cd692383 100644
--- a/Tests/Unit/ObjectSubclassingControllerTests.m
+++ b/Tests/Unit/ObjectSubclassingControllerTests.m
@@ -373,7 +373,7 @@ - (void)testSwiftGetters {
     [subclassingController forwardObjectInvocation:invocation withObject:target];
     __unsafe_unretained PFRelation *returnValue = nil;
     [invocation getReturnValue:&returnValue];
-    XCTAssertTrue([returnValue isKindOfClass:[PFRelation class]]);
+    XCTAssertTrue([returnValue isKindOfClass:[PFRelation class]], @"return value was %@", [returnValue class] ? NSStringFromClass([returnValue class]) : @"nil");
 
     invocation = [self _forwardingInvocationForTarget:target
                                              selector:@selector(badProperty)