diff --git a/homeassistant/components/homematic/__init__.py b/homeassistant/components/homematic/__init__.py
index 97c805aa2ac..747b23bb970 100644
--- a/homeassistant/components/homematic/__init__.py
+++ b/homeassistant/components/homematic/__init__.py
@@ -123,7 +123,8 @@ HM_ATTRIBUTE_SUPPORT = {
     'CURRENT': ['current', {}],
     'VOLTAGE': ['voltage', {}],
     'OPERATING_VOLTAGE': ['voltage', {}],
-    'WORKING': ['working', {0: 'No', 1: 'Yes'}]
+    'WORKING': ['working', {0: 'No', 1: 'Yes'}],
+    'STATE_UNCERTAIN': ['state_uncertain', {}]
 }
 
 HM_PRESS_EVENTS = [
diff --git a/homeassistant/components/homematic/light.py b/homeassistant/components/homematic/light.py
index 72aa9a977d4..f9bc785d3f4 100644
--- a/homeassistant/components/homematic/light.py
+++ b/homeassistant/components/homematic/light.py
@@ -2,8 +2,8 @@
 import logging
 
 from homeassistant.components.light import (
-    ATTR_BRIGHTNESS, ATTR_EFFECT, ATTR_HS_COLOR, SUPPORT_BRIGHTNESS,
-    SUPPORT_COLOR, SUPPORT_EFFECT, Light)
+    ATTR_BRIGHTNESS, ATTR_EFFECT, ATTR_HS_COLOR, ATTR_TRANSITION,
+    SUPPORT_BRIGHTNESS, SUPPORT_COLOR, SUPPORT_EFFECT, Light)
 
 from . import ATTR_DISCOVER_DEVICES, HMDevice
 
@@ -75,6 +75,9 @@ class HMLight(HMDevice, Light):
 
     def turn_on(self, **kwargs):
         """Turn the light on and/or change color or color effect settings."""
+        if ATTR_TRANSITION in kwargs:
+            self._hmdevice.setValue('RAMP_TIME', kwargs[ATTR_TRANSITION])
+
         if ATTR_BRIGHTNESS in kwargs and self._state == "LEVEL":
             percent_bright = float(kwargs[ATTR_BRIGHTNESS]) / 255
             self._hmdevice.set_level(percent_bright, self._channel)