diff --git a/gio/tests/gdbus-connection-slow.c b/gio/tests/gdbus-connection-slow.c
index 0f445d43d..061463f7f 100644
--- a/gio/tests/gdbus-connection-slow.c
+++ b/gio/tests/gdbus-connection-slow.c
@@ -28,6 +28,8 @@
 
 #include "gdbus-tests.h"
 
+#define WAIT_FOR_FLUSH_MSEC 10000
+
 /* all tests rely on a shared mainloop */
 static GMainLoop *loop = NULL;
 
@@ -49,7 +51,7 @@ static gboolean
 test_connection_flush_on_timeout (gpointer user_data)
 {
   guint iteration = GPOINTER_TO_UINT (user_data);
-  g_printerr ("Timeout waiting 1000 msec on iteration %d\n", iteration);
+  g_printerr ("Timeout waiting %d msec on iteration %d\n", WAIT_FOR_FLUSH_MSEC, iteration);
   g_assert_not_reached ();
   return G_SOURCE_REMOVE;
 }
@@ -82,6 +84,16 @@ test_connection_flush (void)
                                                           NULL);
   g_assert_cmpint (signal_handler_id, !=, 0);
 
+  /* We need to wait for the subscription to have actually taken effect
+   * before forking the subprocess, otherwise there is a race condition
+   * between the message bus adding the match rule and the subprocess
+   * sending the signal. If the message bus wins the race, then the test
+   * passes, but if the subprocess wins the race, it will be too late
+   * for this process to receive the signal because it already happened.
+   * The easiest way to avoid this race is to do a round-trip to the
+   * message bus and back. */
+  connection_wait_for_bus (connection);
+
   flush_helper = g_test_get_filename (G_TEST_BUILT, "gdbus-connection-flush-helper", NULL);
   for (n = 0; n < 50; n++)
     {
@@ -108,7 +120,7 @@ test_connection_flush (void)
       g_assert_no_error (error);
       g_assert_true (ret);
 
-      timeout_mainloop_id = g_timeout_add (1000, test_connection_flush_on_timeout, GUINT_TO_POINTER (n));
+      timeout_mainloop_id = g_timeout_add (WAIT_FOR_FLUSH_MSEC, test_connection_flush_on_timeout, GUINT_TO_POINTER (n));
       g_main_loop_run (loop);
       g_source_remove (timeout_mainloop_id);
     }
diff --git a/gio/tests/gdbus-subscribe.c b/gio/tests/gdbus-subscribe.c
index f04ff2063..ce72915ce 100644
--- a/gio/tests/gdbus-subscribe.c
+++ b/gio/tests/gdbus-subscribe.c
@@ -620,35 +620,6 @@ typedef struct
   guint finished_subscription;
 } Fixture;
 
-/* Wait for asynchronous messages from @conn to have been processed
- * by the message bus, as a sequence point so that we can make
- * "happens before" and "happens after" assertions relative to this.
- * The easiest way to achieve this is to call a message bus method that has
- * no arguments and wait for it to return: because the message bus processes
- * messages in-order, anything we sent before this must have been processed
- * by the time this call arrives. */
-static void
-connection_wait_for_bus (GDBusConnection *conn)
-{
-  GError *error = NULL;
-  GVariant *call_result;
-
-  call_result = g_dbus_connection_call_sync (conn,
-                                             DBUS_SERVICE_DBUS,
-                                             DBUS_PATH_DBUS,
-                                             DBUS_INTERFACE_DBUS,
-                                             "GetId",
-                                             NULL,   /* arguments */
-                                             NULL,   /* result type */
-                                             G_DBUS_CALL_FLAGS_NONE,
-                                             -1,
-                                             NULL,
-                                             &error);
-  g_assert_no_error (error);
-  g_assert_nonnull (call_result);
-  g_variant_unref (call_result);
-}
-
 /*
  * Called when the subscriber receives a message from any connection
  * announcing that it has emitted all the signals that it plans to emit.
diff --git a/gio/tests/gdbus-tests.c b/gio/tests/gdbus-tests.c
index 857de0132..7b329fd39 100644
--- a/gio/tests/gdbus-tests.c
+++ b/gio/tests/gdbus-tests.c
@@ -27,6 +27,8 @@
 
 #include "gdbus-tests.h"
 
+#include "gdbusprivate.h"
+
 /* ---------------------------------------------------------------------------------------------------- */
 
 typedef struct
@@ -155,6 +157,40 @@ ensure_gdbus_testserver_up (GDBusConnection *connection,
   g_main_context_pop_thread_default (context);
 }
 
+/*
+ * connection_wait_for_bus:
+ * @conn: A connection
+ *
+ * Wait for asynchronous messages from @conn to have been processed
+ * by the message bus, as a sequence point so that we can make
+ * "happens before" and "happens after" assertions relative to this.
+ * The easiest way to achieve this is to call a message bus method that has
+ * no arguments and wait for it to return: because the message bus processes
+ * messages in-order, anything we sent before this must have been processed
+ * by the time this call arrives.
+ */
+void
+connection_wait_for_bus (GDBusConnection *conn)
+{
+  GError *error = NULL;
+  GVariant *call_result;
+
+  call_result = g_dbus_connection_call_sync (conn,
+                                             DBUS_SERVICE_DBUS,
+                                             DBUS_PATH_DBUS,
+                                             DBUS_INTERFACE_DBUS,
+                                             "GetId",
+                                             NULL,   /* arguments */
+                                             NULL,   /* result type */
+                                             G_DBUS_CALL_FLAGS_NONE,
+                                             -1,
+                                             NULL,
+                                             &error);
+  g_assert_no_error (error);
+  g_assert_nonnull (call_result);
+  g_variant_unref (call_result);
+}
+
 /* ---------------------------------------------------------------------------------------------------- */
 
 typedef struct
diff --git a/gio/tests/gdbus-tests.h b/gio/tests/gdbus-tests.h
index 9cca55656..9cf188f23 100644
--- a/gio/tests/gdbus-tests.h
+++ b/gio/tests/gdbus-tests.h
@@ -119,6 +119,8 @@ GDBusConnection *_g_bus_get_priv (GBusType            bus_type,
 void ensure_gdbus_testserver_up (GDBusConnection *connection,
                                  GMainContext    *context);
 
+void connection_wait_for_bus (GDBusConnection *conn);
+
 G_END_DECLS
 
 #endif /* __TESTS_H__ */