diff --git a/overlay_interface.c b/overlay_interface.c
index 6e906e5d..fa4b6cfe 100644
--- a/overlay_interface.c
+++ b/overlay_interface.c
@@ -489,6 +489,8 @@ overlay_interface_init(const char *name, struct socket_address *addr,
   interface->alarm.stats=&interface_poll_stats;
   
   if (ifconfig->socket_type == SOCK_DGRAM){
+    if (ifconfig->drop_broadcasts || ifconfig->drop_unicasts || ifconfig->drop_packets)
+      FATALF("Invalid interface definition. We only support dropping packets on dummy file interfaces");
     interface->local_echo = 1;
     
     if (overlay_interface_init_socket(interface))
diff --git a/tests/rhizomeprotocol b/tests/rhizomeprotocol
index dec5d4c5..ed83afa0 100755
--- a/tests/rhizomeprotocol
+++ b/tests/rhizomeprotocol
@@ -34,9 +34,7 @@ teardown() {
    report_all_servald_servers
 }
 
-# Called by start_servald_instances for each instance.
-configure_servald_server() {
-   add_servald_interface
+default_config() {
    executeOk_servald config \
       set log.console.level debug \
       set log.console.show_pid on \
@@ -52,6 +50,12 @@ configure_servald_server() {
       set mdp.iftype.wifi.tick_ms 500
 }
 
+# Called by start_servald_instances for each instance.
+configure_servald_server() {
+   add_servald_interface
+   default_config
+}
+
 setup_common() {
    setup_servald
    assert_no_servald_processes
@@ -194,15 +198,18 @@ test_MDPTransportFailOver() {
 
 doc_UnicastTransfer="Rhizome over unicast MDP link"
 setup_UnicastTransfer() {
+   configure_servald_server() {
+      default_config
+      executeOk_servald config \
+         set rhizome.http.enable 0
+   }
    setup_common
-   foreach_instance +A +B \
-     executeOk_servald config \
-       set rhizome.http.enable 0
    set_instance +A
+   add_servald_interface --file
    rhizome_add_file file1 2048
    set_instance +B
+   add_servald_interface --file
    executeOk_servald config \
-      set interfaces.1.file foo \
       set interfaces.1.drop_broadcasts on
    start_servald_instances +A +B
    foreach_instance +A assert_peers_are_instances +B
@@ -297,12 +304,14 @@ test_FileTransferBigMDP() {
 
 doc_FileTransferUnreliableBigMDP="Big new bundle over unreliable MDP transport"
 setup_FileTransferUnreliableBigMDP() {
+   configure_servald_server() {
+      add_servald_interface --file
+      default_config
+      executeOk_servald config \
+         set rhizome.http.enable 0 \
+         set interfaces.1.drop_packets 10
+   }
    setup_common
-   foreach_instance +A +B \
-     executeOk_servald config \
-       set rhizome.http.enable 0 \
-       set interfaces.1.file dummy \
-       set interfaces.1.drop_packets 10
    setup_bigfile_common
 }
 test_FileTransferUnreliableBigMDP() {