diff --git a/extras/conf/udb/Includes/SRB222_linedefs.cfg b/extras/conf/udb/Includes/SRB222_linedefs.cfg
index 039507404..ff25fee2c 100644
--- a/extras/conf/udb/Includes/SRB222_linedefs.cfg
+++ b/extras/conf/udb/Includes/SRB222_linedefs.cfg
@@ -1569,6 +1569,25 @@ udmf
 				type = 15;
 			}
 		}
+
+		30
+		{
+			title = "Waving Flag";
+			prefix = "(30)";
+			arg0
+			{
+				title = "PolyObject ID";
+				type = 14;
+			}
+			arg1
+			{
+				title = "Speed";
+			}
+			arg2
+			{
+				title = "Distance";
+			}
+		}
 	}
 
 	planemove
diff --git a/src/p_setup.c b/src/p_setup.c
index a6c650fc5..2b2efd0f8 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -3081,6 +3081,11 @@ static void P_ConvertBinaryMap(void)
 
 			break;
 		}
+		case 30: //Polyobject - waving flag
+			lines[i].args[0] = tag;
+			lines[i].args[1] = P_AproxDistance(lines[i].dx, lines[i].dy) >> FRACBITS;
+			lines[i].args[2] = sides[lines[i].sidenum[0]].textureoffset >> FRACBITS;
+			break;
 		case 50: //Instantly lower floor on level load
 		case 51: //Instantly raise ceiling on level load
 			lines[i].args[0] = tag;
diff --git a/src/p_spec.c b/src/p_spec.c
index b5f67fedb..b98b244b3 100644
--- a/src/p_spec.c
+++ b/src/p_spec.c
@@ -1189,10 +1189,10 @@ static boolean PolyFlag(line_t *line)
 {
 	polyflagdata_t pfd;
 
-	pfd.polyObjNum = Tag_FGet(&line->tags);
-	pfd.speed = P_AproxDistance(line->dx, line->dy) >> FRACBITS;
+	pfd.polyObjNum = line->args[0];
+	pfd.speed = line->args[1];
 	pfd.angle = R_PointToAngle2(line->v1->x, line->v1->y, line->v2->x, line->v2->y) >> ANGLETOFINESHIFT;
-	pfd.momx = sides[line->sidenum[0]].textureoffset >> FRACBITS;
+	pfd.momx = line->args[2];
 
 	return EV_DoPolyObjFlag(&pfd);
 }