diff --git a/src/SdBus.cpp b/src/SdBus.cpp
index 0fec56b..b523b79 100644
--- a/src/SdBus.cpp
+++ b/src/SdBus.cpp
@@ -48,7 +48,14 @@ int SdBus::sd_bus_send(sd_bus *bus, sd_bus_message *m, uint64_t *cookie)
 {
     std::lock_guard lock(sdbusMutex_);
 
-    return ::sd_bus_send(bus, m, cookie);
+    auto r = ::sd_bus_send(bus, m, cookie);
+    if (r < 0)
+        return r;
+
+    // Make sure long messages are not only stored in outgoing queues but also really sent out
+    ::sd_bus_flush(bus != nullptr ? bus : ::sd_bus_message_get_bus(m));
+
+    return r;
 }
 
 int SdBus::sd_bus_call(sd_bus *bus, sd_bus_message *m, uint64_t usec, sd_bus_error *ret_error, sd_bus_message **reply)
@@ -62,7 +69,14 @@ int SdBus::sd_bus_call_async(sd_bus *bus, sd_bus_slot **slot, sd_bus_message *m,
 {
     std::lock_guard lock(sdbusMutex_);
 
-    return ::sd_bus_call_async(bus, slot, m, callback, userdata, usec);
+    auto r = ::sd_bus_call_async(bus, slot, m, callback, userdata, usec);
+    if (r < 0)
+      return r;
+
+    // Make sure long messages are not only stored in outgoing queues but also really sent out
+    ::sd_bus_flush(bus != nullptr ? bus : ::sd_bus_message_get_bus(m));
+
+    return r;
 }
 
 int SdBus::sd_bus_message_new(sd_bus *bus, sd_bus_message **m, uint8_t type)
diff --git a/tests/integrationtests/DBusSignalsTests.cpp b/tests/integrationtests/DBusSignalsTests.cpp
index 35d1ff8..5ac40d8 100644
--- a/tests/integrationtests/DBusSignalsTests.cpp
+++ b/tests/integrationtests/DBusSignalsTests.cpp
@@ -89,6 +89,18 @@ TEST_F(SdbusTestObject, EmitsSignalWithMapSuccesfully)
     ASSERT_THAT(m_proxy->m_mapFromSignal[1], Eq("one"));
 }
 
+TEST_F(SdbusTestObject, EmitsSignalWithLargeMapSuccesfully)
+{
+  std::map<int32_t, std::string> largeMap;
+  for (int32_t i = 0; i < 20'000; ++i)
+      largeMap.emplace(i, "This is string nr. " + std::to_string(i+1));
+  m_adaptor->emitSignalWithMap(largeMap);
+
+  ASSERT_TRUE(waitUntil(m_proxy->m_gotSignalWithMap));
+  ASSERT_THAT(m_proxy->m_mapFromSignal[0], Eq("This is string nr. 1"));
+  ASSERT_THAT(m_proxy->m_mapFromSignal[1], Eq("This is string nr. 2"));
+}
+
 TEST_F(SdbusTestObject, EmitsSignalWithVariantSuccesfully)
 {
     double d = 3.14;