diff --git a/VERSION b/VERSION
index add683c6..8dfeebea 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-8.3.505
+8.3.506
diff --git a/drc/DRCbasic.c b/drc/DRCbasic.c
index 3cf2e14e..ba434639 100644
--- a/drc/DRCbasic.c
+++ b/drc/DRCbasic.c
@@ -161,6 +161,15 @@ areaCheck(tile, arg)
     if ((rect.r_xbot >= rect.r_xtop) || (rect.r_ybot >= rect.r_ytop))
 	return 0;
 
+    /* Run-length rules are ignored unless the width of the error
+     * exceeds the run-length distance (which is held in the
+     * drcc_cdist entry for the rule).
+     */
+    if (arg->dCD_cptr->drcc_flags & DRC_RUNLENGTH)
+	if (((rect.r_xtop - rect.r_xbot) < arg->dCD_cptr->drcc_cdist) &&
+		((rect.r_ytop - rect.r_ybot) < arg->dCD_cptr->drcc_cdist))
+	    return 0;
+
     /*
      * When Euclidean distance checks are enabled, check for error tiles
      * outside of the perimeter of the circle in the corner extension area
@@ -716,7 +725,6 @@ drcTile (tile, arg)
 				for (i = 0; i < mrd->entries; i++)
 				{
 				    lr = &mrd->rlist[i];
-				    GeoClip(lr, arg->dCD_clip);
 				    if ((lr->r_ytop - lr->r_ybot) > cptr->drcc_cdist)
 				    {
 					triggered = mrd->entries;
@@ -1067,7 +1075,7 @@ drcTile (tile, arg)
 
 		/* Find the rule distances according to the scale factor */
 		dist = cptr->drcc_dist;
-		cdist = cptr->drcc_cdist;
+		cdist = (cptr->drcc_flags & DRC_RUNLENGTH) ? 0 : cptr->drcc_cdist;
 		trigpending = (cptr->drcc_flags & DRC_TRIGGER) ? TRUE : FALSE;
 
 		/* drcc_edgeplane is used to avoid checks on edges	*/
@@ -1119,7 +1127,6 @@ drcTile (tile, arg)
 				for (i = 0; i < mrd->entries; i++)
 				{
 				    lr = &mrd->rlist[i];
-				    GeoClip(lr, arg->dCD_clip);
 				    if ((lr->r_xtop - lr->r_xbot) > cptr->drcc_cdist)
 				    {
 					triggered = mrd->entries;
diff --git a/drc/DRCtech.c b/drc/DRCtech.c
index 17ba586c..1391efdd 100644
--- a/drc/DRCtech.c
+++ b/drc/DRCtech.c
@@ -2135,13 +2135,27 @@ drcMaskSpacing(set1, set2, pmask1, pmask2, wwidth, distance, adjacency,
 			/* reverse order due to the stack property of	*/
 			/* the linked list.				*/
 
-			drcAssign(dpnew, distance, dp->drcc_next, &tmp1, &tmp2,
-				why, distance, DRC_FORWARD, plane2, plane);
-			dptrig = (DRCCookie *) mallocMagic((unsigned)
-				(sizeof (DRCCookie)));
-			drcAssign(dptrig, wwidth, dpnew, set1, set1, why,
-				runlength, DRC_REVERSE | DRC_MAXWIDTH |
-				DRC_TRIGGER | DRC_BENDS, plane2, plane);
+			if (runlength > 0)
+			{
+			    drcAssign(dpnew, distance, dp->drcc_next, &tmp1, &tmp2,
+					why, runlength, DRC_RUNLENGTH |
+					DRC_FORWARD, plane2, plane);
+			    dptrig = (DRCCookie *) mallocMagic((unsigned)
+					(sizeof (DRCCookie)));
+			    drcAssign(dptrig, wwidth, dpnew, set1, set1, why,
+					runlength, DRC_REVERSE | DRC_MAXWIDTH |
+					DRC_TRIGGER | DRC_BENDS, plane2, plane);
+			}
+			else
+			{
+			    drcAssign(dpnew, distance, dp->drcc_next, &tmp1, &tmp2,
+					why, distance, DRC_FORWARD, plane2, plane);
+			    dptrig = (DRCCookie *) mallocMagic((unsigned)
+					(sizeof (DRCCookie)));
+			    drcAssign(dptrig, wwidth, dpnew, set1, set1, why,
+					distance, DRC_REVERSE | DRC_MAXWIDTH |
+					DRC_TRIGGER | DRC_BENDS, plane2, plane);
+			}
 
 			dp->drcc_next = dptrig;
 		    }
@@ -2189,14 +2203,28 @@ drcMaskSpacing(set1, set2, pmask1, pmask2, wwidth, distance, adjacency,
 
 			    /* Assign two coupled rules (see above) */
 
-			    drcAssign(dpnew, distance, dp->drcc_next, &tmp1,
-					&tmp2, why, distance,
+			    if (runlength > 0)
+			    {
+				drcAssign(dpnew, distance, dp->drcc_next, &tmp1,
+					&tmp2, why, runlength, DRC_RUNLENGTH |
 					DRC_REVERSE | DRC_BOTHCORNERS, plane2, plane);
-			    dptrig = (DRCCookie *) mallocMagic((unsigned)
+				dptrig = (DRCCookie *) mallocMagic((unsigned)
 					(sizeof (DRCCookie)));
-			    drcAssign(dptrig, wwidth, dpnew, set1, set1, why,
+				drcAssign(dptrig, wwidth, dpnew, set1, set1, why,
 					runlength, DRC_FORWARD | DRC_MAXWIDTH |
 					DRC_TRIGGER | DRC_BENDS, plane2, plane);
+			    }
+			    else
+			    {
+				drcAssign(dpnew, distance, dp->drcc_next, &tmp1,
+					&tmp2, why, distance,
+					DRC_REVERSE | DRC_BOTHCORNERS, plane2, plane);
+				dptrig = (DRCCookie *) mallocMagic((unsigned)
+					(sizeof (DRCCookie)));
+				drcAssign(dptrig, wwidth, dpnew, set1, set1, why,
+					distance, DRC_FORWARD | DRC_MAXWIDTH |
+					DRC_TRIGGER | DRC_BENDS, plane2, plane);
+			    }
 			    dp->drcc_next = dptrig;
 			}
 			else if (needtrigger)
@@ -2474,7 +2502,7 @@ drcSpacing(argc, argv)
 	{
 	    layers2 = argv[3];
 	    distance = atoi(argv[4]);
-	    runlength = distance;
+	    runlength = -1;
 	    adjacency = argv[5];
 	    why = drcWhyCreate(argv[6]);
 	}
@@ -2488,7 +2516,7 @@ drcSpacing(argc, argv)
 	adjacency = argv[4];
 	wwidth = distance;
 	why = drcWhyCreate(argv[5]);
-	runlength = distance;
+	runlength = -1;
 	if (argc >= 7)
 	{
 	    TechError("Unknown argument in spacing line.\n");
diff --git a/drc/drc.h b/drc/drc.h
index 010feb9b..7ba1e434 100644
--- a/drc/drc.h
+++ b/drc/drc.h
@@ -59,6 +59,7 @@ typedef struct drccookie
  * DRC_BOTHCORNERS:	Must make corner extensions in both directions.
  * DRC_OUTSIDE:		Rule applies only to the outside edge of the rule area.
  * DRC_TRIGGER:		Violation of rule triggers a secondary rule.
+ * DRC_RUNLENGTH:	"cdist" encodes runlength distance, not corner distance.
  *
  * All other flags denote special DRC rules that do not use the standard 4-way
  * edge processing.
@@ -78,11 +79,12 @@ typedef struct drccookie
 #define		DRC_ANGLES_45		0x0400
 #define		DRC_ANGLES_90		0x0800
 #define		DRC_SPLITTILE		0x1000
+#define		DRC_RUNLENGTH		0x2000
 #define 	DRC_NONSTANDARD		(DRC_AREA|DRC_MAXWIDTH|DRC_RECTSIZE\
 					 |DRC_ANGLES_90|DRC_OFFGRID)
 
 /* More flags for indicating what the rule type represents */
-#define		DRC_CIFRULE		0x2000
+#define		DRC_CIFRULE		0x4000
 
 #define	DRC_PENDING			0
 #define DRC_UNPROCESSED 		CLIENTDEFAULT