diff --git a/extras/conf/udb/Includes/SRB222_things.cfg b/extras/conf/udb/Includes/SRB222_things.cfg
index 5cc2851183da85073fd163080b59382a1cbf9cd8..1cb3b41eec46fb515b3b50bada3d519967c84fee 100644
--- a/extras/conf/udb/Includes/SRB222_things.cfg
+++ b/extras/conf/udb/Includes/SRB222_things.cfg
@@ -4778,6 +4778,12 @@ udmf
 		{
 			title = "Slope Vertex";
 			sprite = "internal:vertexslope";
+			arg0
+			{
+				title = "Absolute height?";
+				type = 11;
+				enum = "noyes";
+			}
 		}
 
 		751
diff --git a/src/p_setup.c b/src/p_setup.c
index c6bcded53c9973254a154650446e96cdbb411d3e..cc5b32d739889ec360a9c6c676a60b525b6030e4 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -4915,6 +4915,9 @@ static void P_ConvertBinaryMap(void)
 				// Old behavior if Parameter is 0; add 360 to the angle for each consecutive star post.
 				mapthings[i].args[0] = (mapthings[i].angle/360);
 			break;
+		case 750: //Slope vertex
+			mapthings[i].args[0] = mapthings[i].extrainfo;
+			break;
 		case 753: //Zoom tube waypoint
 			mapthings[i].args[0] = mapthings[i].angle >> 8;
 			mapthings[i].args[1] = mapthings[i].angle & 255;
diff --git a/src/p_slopes.c b/src/p_slopes.c
index bfca153a628c8246fb5c6a2629e6d609115b7a13..c0cc3a98e693fe3b5bd12331c8a452b9101e7ba4 100644
--- a/src/p_slopes.c
+++ b/src/p_slopes.c
@@ -469,7 +469,7 @@ static pslope_t *MakeViaMapthings(INT16 tag1, INT16 tag2, INT16 tag3, UINT8 flag
 		vx[i].x = mt->x << FRACBITS;
 		vx[i].y = mt->y << FRACBITS;
 		vx[i].z = mt->z << FRACBITS;
-		if (!mt->extrainfo)
+		if (!mt->args[0])
 			vx[i].z += R_PointInSubsector(vx[i].x, vx[i].y)->sector->floorheight;
 	}