diff --git a/src/backends/meta-monitor-config-manager.c b/src/backends/meta-monitor-config-manager.c
index 575810b3f..e782f1444 100644
--- a/src/backends/meta-monitor-config-manager.c
+++ b/src/backends/meta-monitor-config-manager.c
@@ -324,7 +324,7 @@ assign_monitor_crtcs (MetaMonitorManager       *manager,
   if (!monitor_mode)
     {
       g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
-                   "Invalid mode %dx%d (%f) for monitor '%s %s'",
+                   "Invalid mode %dx%d (%.3f) for monitor '%s %s'",
                    monitor_mode_spec->width, monitor_mode_spec->height,
                    monitor_mode_spec->refresh_rate,
                    monitor_spec->vendor, monitor_spec->product);