diff --git a/Hive/Backend/BCClient.m b/Hive/Backend/BCClient.m
index 34743344..b37014ed 100644
--- a/Hive/Backend/BCClient.m
+++ b/Hive/Backend/BCClient.m
@@ -25,7 +25,7 @@ @interface BCClient () {
 
 @property (nonatomic, assign) uint64 availableBalance;
 @property (nonatomic, assign) uint64 estimatedBalance;
-@property (nonatomic, strong, readonly) NSMutableSet *transactionObservers;
+@property (nonatomic, strong, readonly) NSHashTable *transactionObservers;
 
 @end
 
@@ -80,7 +80,7 @@ - (instancetype)initWithBaseURL:(NSURL *)URL {
             });
         };
 
-        _transactionObservers = [NSMutableSet new];
+        _transactionObservers = [NSHashTable weakObjectsHashTable];
 
         if (DEBUG_OPTION_ENABLED(TESTING_NETWORK)) {
             bitcoin.testingNetwork = YES;
diff --git a/Hive/Backend/HIExchangeRateService.m b/Hive/Backend/HIExchangeRateService.m
index dc90d1b5..288a583b 100644
--- a/Hive/Backend/HIExchangeRateService.m
+++ b/Hive/Backend/HIExchangeRateService.m
@@ -16,7 +16,7 @@ @interface HIExchangeRateService () {
 }
 
 @property (nonatomic, strong) AFHTTPClient *client;
-@property (nonatomic, strong) NSMutableSet *observers;
+@property (nonatomic, strong) NSHashTable *observers;
 @property (nonatomic, strong) NSMutableDictionary *exchangeRates;
 @property (nonatomic, copy) NSDate *lastUpdate;
 
@@ -41,7 +41,7 @@ - (instancetype)init {
 
     if (self) {
         self.client = [BCClient sharedClient];
-        self.observers = [NSMutableSet new];
+        self.observers = [NSHashTable weakObjectsHashTable];
         self.exchangeRates = [NSMutableDictionary new];
         self.lastUpdate = [NSDate dateWithTimeIntervalSince1970:0];
 
diff --git a/Hive/Backend/HINameFormatService.m b/Hive/Backend/HINameFormatService.m
index c6402b8d..33a3d4f9 100644
--- a/Hive/Backend/HINameFormatService.m
+++ b/Hive/Backend/HINameFormatService.m
@@ -7,7 +7,7 @@
 
 @interface HINameFormatService()
 
-@property (nonatomic, strong) NSMutableSet *observers;
+@property (nonatomic, strong) NSHashTable *observers;
 
 @end
 
@@ -28,7 +28,7 @@ - (id)init {
     self = [super init];
 
     if (self) {
-        _observers = [NSMutableSet new];
+        _observers = [NSHashTable weakObjectsHashTable];
 
         [[NSUserDefaults standardUserDefaults] registerDefaults:@{ LastNameFirstDefaultsKey: @0 }];
         [[NSUserDefaults standardUserDefaults] addObserver:self