diff --git a/ndn-cpp/c/encoding/BinaryXMLDecoder.c b/ndn-cpp/c/encoding/BinaryXMLDecoder.c
index 60040ae..2e65a85 100644
--- a/ndn-cpp/c/encoding/BinaryXMLDecoder.c
+++ b/ndn-cpp/c/encoding/BinaryXMLDecoder.c
@@ -139,7 +139,7 @@
 }
 
 ndn_Error ndn_BinaryXMLDecoder_readBinaryDTagElement
-  (struct ndn_BinaryXMLDecoder *self, unsigned int expectedTag, int allowNull, unsigned char **value, unsigned int *valueLen)
+  (struct ndn_BinaryXMLDecoder *self, unsigned int expectedTag, int allowNull, unsigned char **value, unsigned int *valueLength)
 {
   ndn_Error error;
   if (error = ndn_BinaryXMLDecoder_readElementStartDTag(self, expectedTag))
@@ -153,17 +153,17 @@
       // The binary item is missing, and this is allowed, so read the element close and return a null value.
       ++self->offset;
       *value = 0;
-      *valueLen = 0;
+      *valueLength = 0;
       return 0;
     }
   }
   
   unsigned int itemType;
-  if (error = ndn_BinaryXMLDecoder_decodeTypeAndValue(self, &itemType, valueLen))
+  if (error = ndn_BinaryXMLDecoder_decodeTypeAndValue(self, &itemType, valueLength))
     return error;
   // Ignore itemType.
   *value = self->input + self->offset;
-  self->offset += *valueLen;
+  self->offset += *valueLength;
   
   if (error = ndn_BinaryXMLDecoder_readElementClose(self))
     return error;
@@ -171,20 +171,39 @@
   return 0;
 }
 
+ndn_Error ndn_BinaryXMLDecoder_readOptionalBinaryDTagElement
+  (struct ndn_BinaryXMLDecoder *self, unsigned int expectedTag, int allowNull, unsigned char **value, unsigned int *valueLength)
+{
+  ndn_Error error;
+  int gotExpectedTag;
+  if (error = ndn_BinaryXMLDecoder_peekDTag(self, expectedTag, &gotExpectedTag))
+    return error;
+  if (gotExpectedTag) {
+    if (error = ndn_BinaryXMLDecoder_readBinaryDTagElement(self, expectedTag, allowNull, value, valueLength))
+      return error;
+  }
+  else {
+    *value = 0;
+    *valueLength = 0;
+  }  
+  
+  return 0;
+}
+
 ndn_Error ndn_BinaryXMLDecoder_readUDataDTagElement
-  (struct ndn_BinaryXMLDecoder *self, unsigned int expectedTag, unsigned char **value, unsigned int *valueLen)
+  (struct ndn_BinaryXMLDecoder *self, unsigned int expectedTag, unsigned char **value, unsigned int *valueLength)
 {
   ndn_Error error;
   if (error = ndn_BinaryXMLDecoder_readElementStartDTag(self, expectedTag))
     return error;
     
   unsigned int itemType;
-  if (error = ndn_BinaryXMLDecoder_decodeTypeAndValue(self, &itemType, valueLen))
+  if (error = ndn_BinaryXMLDecoder_decodeTypeAndValue(self, &itemType, valueLength))
     return error;
   if (itemType != ndn_BinaryXML_UDATA)
     return NDN_ERROR_item_is_not_UDATA;
   *value = self->input + self->offset;
-  self->offset += *valueLen;
+  self->offset += *valueLength;
   
   if (error = ndn_BinaryXMLDecoder_readElementClose(self))
     return error;
diff --git a/ndn-cpp/c/encoding/BinaryXMLDecoder.h b/ndn-cpp/c/encoding/BinaryXMLDecoder.h
index 0c1427e..2686e81 100644
--- a/ndn-cpp/c/encoding/BinaryXMLDecoder.h
+++ b/ndn-cpp/c/encoding/BinaryXMLDecoder.h
@@ -70,13 +70,28 @@
  * @param allowNull 1 if the binary item may be missing
  * @param value output a pointer to the binary data inside self's input buffer. However, if allowNull is 1 and the
  * binary data item is absent, then return 0.
- * @param valueLen output the length of the binary data. However, if allowNull is 1 and the
+ * @param valueLength output the length of the binary data. However, if allowNull is 1 and the
  * binary data item is absent, then return 0.
  * @return 0 for success, else an error code, including an error if not the expected tag, or if allowNull is 0
  * and the binary data is absent
  */
 ndn_Error ndn_BinaryXMLDecoder_readBinaryDTagElement
-  (struct ndn_BinaryXMLDecoder *self, unsigned int expectedTag, int allowNull, unsigned char **value, unsigned int *valueLen);
+  (struct ndn_BinaryXMLDecoder *self, unsigned int expectedTag, int allowNull, unsigned char **value, unsigned int *valueLength);
+
+/**
+ * Peek at the next element and if it is the expectedTag, call ndn_BinaryXMLDecoder_readBinaryDTagElement.
+ * Otherwise, set value and valueLength to 0.
+ * @param self pointer to the ndn_BinaryXMLDecoder struct
+ * @param expectedTag the expected value for DTAG
+ * @param allowNull 1 if the binary item may be missing
+ * @param value output a pointer to the binary data inside self's input buffer. However, if allowNull is 1 and the
+ * binary data item is absent, then return 0.
+ * @param valueLength output the length of the binary data. However, if allowNull is 1 and the
+ * binary data item is absent, then return 0.
+ * @return 0 for success, else an error code, including if allowNull is 0 and the binary data is absent
+ */
+ndn_Error ndn_BinaryXMLDecoder_readOptionalBinaryDTagElement
+  (struct ndn_BinaryXMLDecoder *self, unsigned int expectedTag, int allowNull, unsigned char **value, unsigned int *valueLength);
 
 /**
  * Decode the header from self's input starting at offset, expecting the type to be DTAG and the value to be expectedTag.
@@ -85,11 +100,11 @@
  * @param self pointer to the ndn_BinaryXMLDecoder struct
  * @param expectedTag the expected value for DTAG
  * @param value output a pointer to the binary data inside self's input buffer.
- * @param valueLen output the length of the binary data.
+ * @param valueLength output the length of the binary data.
  * @return 0 for success, else an error code, including an error if not the expected tag, or if the item is not UDATA.
  */
 ndn_Error ndn_BinaryXMLDecoder_readUDataDTagElement
-  (struct ndn_BinaryXMLDecoder *self, unsigned int expectedTag, unsigned char **value, unsigned int *valueLen);
+  (struct ndn_BinaryXMLDecoder *self, unsigned int expectedTag, unsigned char **value, unsigned int *valueLength);
 
 /**
  * Decode the header from self's input starting at offset, expecting the type to be DTAG and the value to be expectedTag.
diff --git a/ndn-cpp/c/encoding/BinaryXMLInterest.c b/ndn-cpp/c/encoding/BinaryXMLInterest.c
index a6e4ea8..6b02176 100644
--- a/ndn-cpp/c/encoding/BinaryXMLInterest.c
+++ b/ndn-cpp/c/encoding/BinaryXMLInterest.c
@@ -241,17 +241,9 @@
   else
     interest->interestLifetime = -1;
   
-  if (error = ndn_BinaryXMLDecoder_peekDTag(decoder, ndn_BinaryXML_DTag_Nonce, &gotExpectedTag))
+  if (error = ndn_BinaryXMLDecoder_readOptionalBinaryDTagElement
+      (decoder, ndn_BinaryXML_DTag_Nonce, 0, &interest->nonce, &interest->nonceLength))
     return error;
-  if (gotExpectedTag) {
-    if (error = ndn_BinaryXMLDecoder_readBinaryDTagElement
-        (decoder, ndn_BinaryXML_DTag_Nonce, 0, &interest->nonce, &interest->nonceLength))
-      return error;
-  }
-  else {
-    interest->nonce = 0;
-    interest->nonceLength = 0;
-  }
 
   if (error = ndn_BinaryXMLDecoder_readElementClose(decoder))
     return error;