diff --git a/plugins/power/gsd-power-manager.c b/plugins/power/gsd-power-manager.c
index 490b5536d92af2cdab8f88cae391dafd038d2370..2355111675ddf4dd621bf9187f786d55240bf337 100644
--- a/plugins/power/gsd-power-manager.c
+++ b/plugins/power/gsd-power-manager.c
@@ -1240,7 +1240,7 @@ shell_brightness_set_auto_target_cb (GObject      *source_object,
 
 static void
 shell_brightness_set_auto_target (GsdPowerManager *manager,
-                                  float            target)
+                                  double           target)
 {
         if (!manager->shell_brightness_proxy)
                 return;
@@ -2979,7 +2979,7 @@ iio_proxy_changed (GsdPowerManager *manager)
                  manager->ambient_accumulator);
         pc = manager->ambient_accumulator;
 
-        shell_brightness_set_auto_target (manager, pc / 100);
+        shell_brightness_set_auto_target (manager, pc / 100.0);
 
         /* Assume setting worked. */
         manager->ambient_percentage_old = pc;
@@ -3108,7 +3108,7 @@ gsd_power_manager_startup (GApplication *app)
         manager->ambient_norm_required = TRUE;
         manager->ambient_accumulator = -1.f;
         manager->ambient_norm_value = -1.f;
-        manager->ambient_percentage_old = -1.f;
+        manager->ambient_percentage_old = 75.0f;
         manager->ambient_last_absolute = -1.f;
         manager->ambient_last_time = 0;