diff --git a/core/src/main/java/com/google/bitcoin/protocols/payments/PaymentSession.java b/core/src/main/java/com/google/bitcoin/protocols/payments/PaymentSession.java
index b15ae38f..9414064f 100644
--- a/core/src/main/java/com/google/bitcoin/protocols/payments/PaymentSession.java
+++ b/core/src/main/java/com/google/bitcoin/protocols/payments/PaymentSession.java
@@ -22,6 +22,7 @@ import com.google.bitcoin.script.ScriptBuilder;
 import com.google.bitcoin.uri.BitcoinURI;
 import com.google.bitcoin.utils.Threading;
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Joiner;
 import com.google.common.collect.Lists;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.ListeningExecutorService;
@@ -226,26 +227,30 @@ public class PaymentSession {
      * Message returned by the merchant in response to a Payment message.
      */
     public class Ack {
-        private String memo = "";
+        @Nullable private String memo;
 
-        Ack(String memo) {
+        Ack(@Nullable String memo) {
             this.memo = memo;
         }
 
         /**
          * Returns the memo included by the merchant in the payment ack. This message is typically displayed to the user
-         * as a notification (e.g. "Your payment was received and is being processed").
+         * as a notification (e.g. "Your payment was received and is being processed"). If none was provided, returns
+         * null.
          */
-        public String getMemo() {
+        @Nullable public String getMemo() {
             return memo;
         }
     }
 
     /**
-     * Returns the memo included by the merchant in the payment request.
+     * Returns the memo included by the merchant in the payment request, or null if not found.
      */
-    public String getMemo() {
-        return paymentDetails.getMemo();
+    @Nullable public String getMemo() {
+        if (paymentDetails.hasMemo())
+            return paymentDetails.getMemo();
+        else
+            return null;
     }
 
     /**
@@ -373,7 +378,7 @@ public class PaymentSession {
                 InputStream inStream = connection.getInputStream();
                 Protos.PaymentACK.Builder paymentAckBuilder = Protos.PaymentACK.newBuilder().mergeFrom(inStream);
                 Protos.PaymentACK paymentAck = paymentAckBuilder.build();
-                String memo = "";
+                String memo = null;
                 if (paymentAck.hasMemo())
                     memo = paymentAck.getMemo();
                 return new Ack(memo);
@@ -420,8 +425,8 @@ public class PaymentSession {
                 else if (pair.getType().equals(RFC4519Style.c))
                     country = val;
             }
-            if (org != null && location != null && country != null) {
-                return org + ", " + location + ", " + country;
+            if (org != null) {
+                return Joiner.on(", ").skipNulls().join(org, location, country);
             } else {
                 if (commonName == null)
                     throw new PaymentRequestException.PkiVerificationException("Could not find any identity info for root CA");
@@ -616,10 +621,20 @@ public class PaymentSession {
             }
             // This won't ever happen in practice. It would only happen if the user provided outputs
             // that are obviously invalid. Still, we don't want to silently overflow.
-            if (totalValue.compareTo(BigInteger.valueOf(Long.MAX_VALUE)) > 0)
+            if (totalValue.compareTo(NetworkParameters.MAX_MONEY) > 0)
                 throw new PaymentRequestException.InvalidOutputs("The outputs are way too big.");
         } catch (InvalidProtocolBufferException e) {
             throw new PaymentRequestException(e);
         }
     }
+
+    /** Returns the protobuf that this object was instantiated with. */
+    public Protos.PaymentRequest getPaymentRequest() {
+        return paymentRequest;
+    }
+
+    /** Returns the protobuf that describes the payment to be made. */
+    public Protos.PaymentDetails getPaymentDetails() {
+        return paymentDetails;
+    }
 }