diff --git a/homeassistant/components/modbus.py b/homeassistant/components/modbus.py
index 3bf6cbf031a..1f1363f2060 100644
--- a/homeassistant/components/modbus.py
+++ b/homeassistant/components/modbus.py
@@ -59,7 +59,7 @@ ATTR_VALUE = "value"
 SERVICE_WRITE_REGISTER_SCHEMA = vol.Schema({
     vol.Required(ATTR_UNIT): cv.positive_int,
     vol.Required(ATTR_ADDRESS): cv.positive_int,
-    vol.Required(ATTR_VALUE): cv.positive_int
+    vol.Required(ATTR_VALUE): vol.All(cv.ensure_list, [cv.positive_int])
 })