diff --git a/Classes/ProductLoader.m b/Classes/ProductLoader.m
index 393c92c..2a3160f 100644
--- a/Classes/ProductLoader.m
+++ b/Classes/ProductLoader.m
@@ -42,7 +42,14 @@ - (void)request:(SKRequest *)request didFailWithError:(NSError *)error
 
 - (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response
 {
-    _product = response.products[0];    
+    if (response.products.count == 0)
+    {
+        _error = [NSError errorWithDomain:@"SimplePurchaseErrorDomain" code:1 userInfo:@{NSLocalizedDescriptionKey: @"Product id is unknown."}];
+    }
+    else
+    {
+        _product = response.products[0];
+    }
 }
 
 - (void)requestDidFinish:(SKRequest *)request
diff --git a/Classes/Purchaser.m b/Classes/Purchaser.m
index 642a9f7..692aa5e 100644
--- a/Classes/Purchaser.m
+++ b/Classes/Purchaser.m
@@ -64,8 +64,6 @@ - (void)paymentQueue:(SKPaymentQueue *)queue updatedTransactions:(NSArray *)tran
         
         if ([self transactionIsSuccess:t])
             [self notifyObserversForProduct:t.payment.productIdentifier transaction:t];
-        
-        [[SKPaymentQueue defaultQueue] finishTransaction:t];
     }
 }
 
diff --git a/Classes/SimplePurchase.h b/Classes/SimplePurchase.h
index 5a33e4d..890a4fb 100644
--- a/Classes/SimplePurchase.h
+++ b/Classes/SimplePurchase.h
@@ -6,5 +6,6 @@
 
 + (void)addObserverForProduct:(NSString *)productId block:(void(^)(SKPaymentTransaction *transaction))block;
 + (void)buyProduct:(NSString *)productId block:(void(^)(NSError *error))block;
++ (void)finishTransaction:(SKPaymentTransaction*)t;
 
 @end
diff --git a/Classes/SimplePurchase.m b/Classes/SimplePurchase.m
index f85dec7..d1736d6 100644
--- a/Classes/SimplePurchase.m
+++ b/Classes/SimplePurchase.m
@@ -22,4 +22,9 @@ + (void)buyProduct:(NSString *)productId block:(void(^)(NSError *error))block
     [_purchaser buyProduct:productId block:block];
 }
 
++ (void)finishTransaction:(SKPaymentTransaction*)t
+{
+    [[SKPaymentQueue defaultQueue] finishTransaction:t];
+}
+
 @end