diff --git a/deps/rabbit/src/rabbit_disk_monitor.erl b/deps/rabbit/src/rabbit_disk_monitor.erl
index e095481353..28b4cb3eba 100644
--- a/deps/rabbit/src/rabbit_disk_monitor.erl
+++ b/deps/rabbit/src/rabbit_disk_monitor.erl
@@ -180,8 +180,12 @@ code_change(_OldVsn, State, _Extra) ->
 
 safe_ets_lookup(Key, Default) ->
     try
-        [{Key, Value}] = ets:lookup(?ETS_NAME, Key),
-        Value
+        case ets:lookup(?ETS_NAME, Key) of
+            [{Key, Value}] ->
+                Value;
+            [] ->
+                Default
+        end
     catch
         error:badarg ->
             Default
diff --git a/deps/rabbit/test/unit_disk_monitor_mocks_SUITE.erl b/deps/rabbit/test/unit_disk_monitor_mocks_SUITE.erl
index 80fa3d2e09..ae16cbb379 100644
--- a/deps/rabbit/test/unit_disk_monitor_mocks_SUITE.erl
+++ b/deps/rabbit/test/unit_disk_monitor_mocks_SUITE.erl
@@ -88,7 +88,7 @@ disk_monitor_enable1(_Config) ->
     application:set_env(rabbit, disk_monitor_failure_retry_interval, 100),
     ok = rabbit_sup:stop_child(rabbit_disk_monitor_sup),
     ok = rabbit_sup:start_delayed_restartable_child(rabbit_disk_monitor, [1000]),
-    undefined = rabbit_disk_monitor:get_disk_free(),
+    unknown = rabbit_disk_monitor:get_disk_free(),
     Cmd = case os:type() of
               {win32, _} -> " Le volume dans le lecteur C n’a pas de nom.\n"
                             " Le numéro de série du volume est 707D-5BDC\n"