diff --git a/specs/udmf_zdoom.txt b/specs/udmf_zdoom.txt
index 5bac0bb4d..d56b8ed0b 100644
--- a/specs/udmf_zdoom.txt
+++ b/specs/udmf_zdoom.txt
@@ -113,6 +113,7 @@ Note: All <bool> fields default to false unless mentioned otherwise.
       blockprojectiles = <bool>;// Line blocks all projectiles
       blockuse = <bool>;        // Line blocks all use actions
       blocksight = <bool>;      // Line blocks monster line of sight
+      locknumber = <int>;       // Line special is locked
       arg0str = <string>;       // Alternate string-based version of arg0
 
       * Note about arg0str
@@ -312,6 +313,9 @@ Added Sector_Set3DFloor to list of specials that need to be handled for line ID
 Added arg0str linedef property.
 Standardized whitespace.
 
+1.19 24.02.2012
+Added back locknumber property.
+
 ===============================================================================
 EOF
 ===============================================================================