diff --git a/src/include/unit.h b/src/include/unit.h
index 816e9e97c..5f340f393 100644
--- a/src/include/unit.h
+++ b/src/include/unit.h
@@ -445,7 +445,7 @@ extern void UnitLost(const Unit* unit);
 extern void UpdateForNewUnit(const Unit* unit,int upgrade);
     /// FIXME: more docu
 extern void NearestOfUnit(const Unit* unit,int tx,int ty,int *dx,int *dy);
-    /// FIXME: more docu
+    /// Returns true, if unit is visible on current map view.
 extern int UnitVisible(const Unit* unit);
     /// FIXME: more docu
 extern int CheckUnitToBeDrawn(const Unit* unit);