diff --git a/bacnet-stack/demo/handler/h_rp.c b/bacnet-stack/demo/handler/h_rp.c
index 96dedf41..a8027332 100644
--- a/bacnet-stack/demo/handler/h_rp.c
+++ b/bacnet-stack/demo/handler/h_rp.c
@@ -109,7 +109,7 @@ void handler_read_property(
             data.array_index,
             &error_class,
             &error_code);
-          if (len > 0)
+          if (len >= 0)
           {
             // encode the APDU portion of the packet
             data.application_data = &Temp_Buf[0];
@@ -138,7 +138,7 @@ void handler_read_property(
             data.array_index,
             &error_class,
             &error_code);
-          if (len > 0)
+          if (len >= 0)
           {
             // encode the APDU portion of the packet
             data.application_data = &Temp_Buf[0];
@@ -167,7 +167,7 @@ void handler_read_property(
             data.array_index,
             &error_class,
             &error_code);
-          if (len > 0)
+          if (len >= 0)
           {
             // encode the APDU portion of the packet
             data.application_data = &Temp_Buf[0];
@@ -197,7 +197,7 @@ void handler_read_property(
             data.array_index,
             &error_class,
             &error_code);
-          if (len > 0)
+          if (len >= 0)
           {
             // encode the APDU portion of the packet
             data.application_data = &Temp_Buf[0];
diff --git a/bacnet-stack/demo/object/ai.c b/bacnet-stack/demo/object/ai.c
index c351c69e..38c6f1a7 100644
--- a/bacnet-stack/demo/object/ai.c
+++ b/bacnet-stack/demo/object/ai.c
@@ -61,6 +61,7 @@ uint32_t Analog_Input_Index_To_Instance(unsigned index)
   return index;
 }
 
+/* return apdu length, or -1 on error */
 int Analog_Input_Encode_Property_APDU(
   uint8_t *apdu,
   uint32_t object_instance,
@@ -115,6 +116,7 @@ int Analog_Input_Encode_Property_APDU(
     default:
       *error_class = ERROR_CLASS_PROPERTY;
       *error_code = ERROR_CODE_UNKNOWN_PROPERTY;
+      apdu_len = -1;
       break;
   }
 
@@ -147,7 +149,7 @@ void testAnalogInput(Test * pTest)
     BACNET_ARRAY_ALL,
     &error_class,
     &error_code);
-  ct_test(pTest, len != 0);
+  ct_test(pTest, len >= 0);
   len = decode_tag_number_and_value(&apdu[0], &tag_number, &len_value);
   ct_test(pTest, tag_number == BACNET_APPLICATION_TAG_OBJECT_ID);
   len = decode_object_id(&apdu[len],
diff --git a/bacnet-stack/demo/object/ao.c b/bacnet-stack/demo/object/ao.c
index edd056ff..85126f28 100644
--- a/bacnet-stack/demo/object/ao.c
+++ b/bacnet-stack/demo/object/ao.c
@@ -141,6 +141,7 @@ static float Analog_Output_Present_Value(uint32_t object_instance)
   return value;
 }
 
+/* return apdu len, or -1 on error */
 int Analog_Output_Encode_Property_APDU(
   uint8_t *apdu,
   uint32_t object_instance,
@@ -223,7 +224,7 @@ int Analog_Output_Encode_Property_APDU(
           {
             *error_class = ERROR_CLASS_SERVICES;
             *error_code = ERROR_CODE_NO_SPACE_FOR_OBJECT;
-            apdu_len = 0;
+            apdu_len = -1;
             break;
           }
         }
@@ -245,6 +246,7 @@ int Analog_Output_Encode_Property_APDU(
         {
           *error_class = ERROR_CLASS_PROPERTY;
           *error_code = ERROR_CODE_INVALID_ARRAY_INDEX;
+          apdu_len = -1;
         }
       }
     
@@ -256,6 +258,7 @@ int Analog_Output_Encode_Property_APDU(
     default:
       *error_class = ERROR_CLASS_PROPERTY;
       *error_code = ERROR_CODE_UNKNOWN_PROPERTY;
+      apdu_len = -1;
       break;
   }
 
diff --git a/bacnet-stack/demo/object/bacfile.c b/bacnet-stack/demo/object/bacfile.c
index bad1a68b..71442acf 100644
--- a/bacnet-stack/demo/object/bacfile.c
+++ b/bacnet-stack/demo/object/bacfile.c
@@ -144,6 +144,7 @@ static unsigned bacfile_file_size(uint32_t object_instance)
   return file_size;
 }
 
+/* return the number of bytes used, or -1 on error */
 int bacfile_encode_property_apdu(
   uint8_t *apdu,
   uint32_t object_instance,
@@ -215,6 +216,7 @@ int bacfile_encode_property_apdu(
     default:
       *error_class = ERROR_CLASS_PROPERTY;
       *error_code = ERROR_CODE_UNKNOWN_PROPERTY;
+      apdu_len = -1;
       break;
   }
 
diff --git a/bacnet-stack/demo/object/device.c b/bacnet-stack/demo/object/device.c
index a34a3ffd..fc2d1bf2 100644
--- a/bacnet-stack/demo/object/device.c
+++ b/bacnet-stack/demo/object/device.c
@@ -379,7 +379,7 @@ bool Device_Object_List_Identifier(unsigned array_index,
   return status;
 }
 
-// return the length of the apdu encoded
+// return the length of the apdu encoded or -1 for error
 int Device_Encode_Property_APDU(
   uint8_t *apdu,
   BACNET_PROPERTY_ID property,
@@ -514,7 +514,7 @@ int Device_Encode_Property_APDU(
             {
               *error_class = ERROR_CLASS_SERVICES;
               *error_code = ERROR_CODE_NO_SPACE_FOR_OBJECT;
-              apdu_len = 0;
+              apdu_len = -1;
               break;
             }
           }
@@ -523,7 +523,7 @@ int Device_Encode_Property_APDU(
             // error: internal error?
             *error_class = ERROR_CLASS_SERVICES;
             *error_code = ERROR_CODE_OTHER;
-            apdu_len = 0;
+            apdu_len = -1;
             break;
           }
         }
@@ -536,6 +536,7 @@ int Device_Encode_Property_APDU(
         {
           *error_class = ERROR_CLASS_PROPERTY;
           *error_code = ERROR_CODE_INVALID_ARRAY_INDEX;
+          apdu_len = -1;
         }
       }
       break;
@@ -554,13 +555,12 @@ int Device_Encode_Property_APDU(
       apdu_len = encode_tagged_unsigned(&apdu[0], Number_Of_APDU_Retries);
       break;
     case PROP_DEVICE_ADDRESS_BINDING:
-      apdu_len += encode_opening_tag(&apdu[0], 3);
-      /* put the list here, if it exists */
-      apdu_len += encode_closing_tag(&apdu[apdu_len], 3);
+      /* encode the list here, if it exists */
       break;
     default:
       *error_class = ERROR_CLASS_PROPERTY;
       *error_code = ERROR_CODE_UNKNOWN_PROPERTY;
+      apdu_len = -1;
       break;
   }