diff --git a/README b/README
index 35dc285..69ca8ad 100644
--- a/README
+++ b/README
@@ -132,9 +132,10 @@ vicious.widgets.cpufreq
 vicious.widgets.thermal
   - provides temperature levels of ACPI and coretemp thermal zones
   - takes the thermal zone as an argument, i.e. "thermal_zone0", or a
-    table with 1st field as thermal zone and 2nd as data source -
-    available data sources are "proc", "core" and "sys" - which is the
-    default when only the zone is provided
+    table with 1st field as thermal zone, 2nd as data source -
+    available data sources are "proc", "core" and "sys" (which is the
+    default when only the zone is provided) and 3rd optional argument
+    as a temperature input file to read
   - returns 1st value as temperature of requested thermal zone
 
 vicious.widgets.uptime