diff --git a/docs/unit.rst b/docs/unit.rst
index 003e12df71f91e2034b6878c69676cf71866d8f9..b5e94e274ccf8c9e37afaf2f3a852dde363f4adb 100644
--- a/docs/unit.rst
+++ b/docs/unit.rst
@@ -26,9 +26,15 @@ Unit
    .. autoattribute:: id 
    .. autoattribute:: is_alive 
    .. autoattribute:: is_being_constructed 
+      
+      Returns build_progress > 0
+
    .. autoattribute:: is_burrowed 
    .. autoattribute:: is_cloaked 
    .. autoattribute:: is_completed 
+
+      Returns build_progress >= 1
+
    .. autoattribute:: is_constructing 
    .. autoattribute:: is_flying 
    .. autoattribute:: is_idle