diff --git a/specs/udmf_zdoom.txt b/specs/udmf_zdoom.txt
index ebc831d574..b82ea4a021 100644
--- a/specs/udmf_zdoom.txt
+++ b/specs/udmf_zdoom.txt
@@ -386,6 +386,7 @@ Note: All <bool> fields default to false unless mentioned otherwise.
 
       lm_sampledist_floor = <int>;      // ZDRay customizable sampling distance for this sector's floor. Defines the map units each lightmap texel covers. Must be in powers of two. Default = 0
       lm_sampledist_ceiling = <int>;    // ZDRay customizable sampling distance for this sector's ceiling. Defines the map units each lightmap texel covers. Must be in powers of two. Default = 0
+      lm_dynamic = <bool>;              // ZDRay marks a sector's lightmaps as dynamic so that they may be updated in realtime (used for flickering lights, changing a lightmap light's position, color etc). Default = false
    }
 
    thing
@@ -416,8 +417,9 @@ Note: All <bool> fields default to false unless mentioned otherwise.
       scale = <float>;          // Vertical and horizontal scaling on thing. Default = 0 (ignored).
       floatbobphase = <int>;    // Sets the thing's floatbobphase. Valid phase values are 0-63. Default = -1 (use actor class default).
 
-      lm_sampledistance = <int>;    // ZDRay lightmap sample distance for the entire map. Defines the map units each lightmap texel covers. Must be in powers of two. Default = 16
-      lm_suncolor = <string>;       // ZDRay lightmap sun color in hex. Default: "FFFFFF"
+      lm_sampledist = <int>;        // ZDRay lightmap sample distance for the entire map. Defines the map units each lightmap texel covers. Must be in powers of two. Default = 8
+      lm_suncolor = <string>;       // ZDRay lightmap sun color in hex. Default = "FFFFFF"
+      sourceradius = <float>;       // ZDRay lightmap light soft shadow amount. Higher values produce softer shadows. Default = 5.0
 
       * Note about arg0str
 
diff --git a/src/maploader/udmf.cpp b/src/maploader/udmf.cpp
index ea3e03b878..6601bf1f69 100644
--- a/src/maploader/udmf.cpp
+++ b/src/maploader/udmf.cpp
@@ -792,7 +792,7 @@ public:
 				break;
 
 			case NAME_lm_suncolor:
-			case NAME_lm_sampledistance:
+			case NAME_lm_sampledist:
 				CHECK_N(Zd | Zdt)
 					break;
 
diff --git a/src/namedef_custom.h b/src/namedef_custom.h
index 2da881531d..57dbefcba9 100644
--- a/src/namedef_custom.h
+++ b/src/namedef_custom.h
@@ -858,8 +858,10 @@ xx(lm_sampledist_mid)
 xx(lm_sampledist_bot)
 xx(lm_sampledist_floor)
 xx(lm_sampledist_ceiling)
+xx(lm_dynamic)
 xx(lm_suncolor)
-xx(lm_sampledistance)
+xx(lm_sampledist)
+xx(sourceradius)
 
 xx(skew_bottom_type)
 xx(skew_middle_type)