diff --git a/src/apps/snmp/snmp_threadsync.c b/src/apps/snmp/snmp_threadsync.c
index cfcfb274..6947c52f 100644
--- a/src/apps/snmp/snmp_threadsync.c
+++ b/src/apps/snmp/snmp_threadsync.c
@@ -55,7 +55,11 @@ threadsync_get_value_synced(void *ctx)
 {
   struct threadsync_data *call_data = (struct threadsync_data *)ctx;
 
-  call_data->retval.s16 = call_data->proxy_instance.get_value(&call_data->proxy_instance, call_data->arg1.value);
+  if (call_data->proxy_instance.get_value != NULL) {
+    call_data->retval.s16 = call_data->proxy_instance.get_value(&call_data->proxy_instance, call_data->arg1.value);
+  } else {
+    call_data->retval.s16 = -1;
+  }
 
   sys_sem_signal(&call_data->threadsync_node->instance->sem);
 }
@@ -76,7 +80,11 @@ threadsync_set_test_synced(void *ctx)
 {
   struct threadsync_data *call_data = (struct threadsync_data *)ctx;
 
-  call_data->retval.err = call_data->proxy_instance.set_test(&call_data->proxy_instance, call_data->arg2.len, call_data->arg1.value);
+  if (call_data->proxy_instance.set_test != NULL) {
+    call_data->retval.err = call_data->proxy_instance.set_test(&call_data->proxy_instance, call_data->arg2.len, call_data->arg1.value);
+  } else {
+    call_data->retval.err = SNMP_ERR_NOSUCHINSTANCE;
+  }
 
   sys_sem_signal(&call_data->threadsync_node->instance->sem);
 }
@@ -98,7 +106,11 @@ threadsync_set_value_synced(void *ctx)
 {
   struct threadsync_data *call_data = (struct threadsync_data *)ctx;
 
-  call_data->retval.err = call_data->proxy_instance.set_value(&call_data->proxy_instance, call_data->arg2.len, call_data->arg1.value);
+  if (call_data->proxy_instance.set_value != NULL) {
+    call_data->retval.err = call_data->proxy_instance.set_value(&call_data->proxy_instance, call_data->arg2.len, call_data->arg1.value);
+  } else {
+    call_data->retval.err = SNMP_ERR_NOSUCHINSTANCE;
+  }
 
   sys_sem_signal(&call_data->threadsync_node->instance->sem);
 }