diff --git a/src/apps/snmp/snmp_msg.c b/src/apps/snmp/snmp_msg.c
index 562ec60e..0b6693a7 100644
--- a/src/apps/snmp/snmp_msg.c
+++ b/src/apps/snmp/snmp_msg.c
@@ -451,10 +451,10 @@ snmp_process_varbind(struct snmp_request *request, struct snmp_varbind *vb, u8_t
     }
   } else {
     s16_t len = node_instance.get_value(&node_instance, vb->value);
-    vb->type = node_instance.asn1_type;
 
     if (len >= 0) {
       vb->value_len = (u16_t)len; /* cast is OK because we checked >= 0 above */
+      vb->type = node_instance.asn1_type;
 
       LWIP_ASSERT("SNMP_MAX_VALUE_SIZE is configured too low", (vb->value_len & ~SNMP_GET_VALUE_RAW_DATA) <= SNMP_MAX_VALUE_SIZE);
       err = snmp_append_outbound_varbind(&request->outbound_pbuf_stream, vb);
diff --git a/src/include/lwip/apps/snmp_core.h b/src/include/lwip/apps/snmp_core.h
index 9e7a518c..6021c722 100644
--- a/src/include/lwip/apps/snmp_core.h
+++ b/src/include/lwip/apps/snmp_core.h
@@ -191,7 +191,7 @@ typedef snmp_err_t (*node_instance_set_test_method)(struct snmp_node_instance*,
 typedef snmp_err_t (*node_instance_set_value_method)(struct snmp_node_instance*, u16_t, void*);
 typedef void (*node_instance_release_method)(struct snmp_node_instance*);
 
-#define SNMP_GET_VALUE_RAW_DATA 0x8000
+#define SNMP_GET_VALUE_RAW_DATA 0x4000  /* do not use 0x8000 because return value of node_instance_get_value_method is signed16 and 0x8000 would be the signed bit */
 
 /** SNMP node instance */
 struct snmp_node_instance