diff --git a/VERSION b/VERSION
index 3d7c223d..19951506 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-8.3.271
+8.3.272
diff --git a/database/DBcellcopy.c b/database/DBcellcopy.c
index 9f685e8b..f8f147cf 100644
--- a/database/DBcellcopy.c
+++ b/database/DBcellcopy.c
@@ -397,6 +397,7 @@ DBCellGenerateSubstrate(scx, subType, notSubMask, subShieldMask, targetDef)
     int plane;
     Rect rect;
     TileTypeBitMask allButSubMask;
+    TileTypeBitMask defaultSubTypeMask;
     int dbEraseSubFunc();
     int dbPaintSubFunc();
     int dbEraseNonSub();
@@ -417,9 +418,15 @@ DBCellGenerateSubstrate(scx, subType, notSubMask, subShieldMask, targetDef)
     csd.csd_pNum = plane;
     csd.csd_modified = FALSE;
 
-    /* First paint the substrate type in the temporary plane over the	*/
-    /* area of all substrate shield types.				*/
+    /* The substrate type will be redefined to denote only areas of	*/
+    /* isolated substrate.  The first step is to erase the default	*/
+    /* substrate everywhere so that it can be regenerated automatically	*/
     /* Note: xMask is always zero, as this is only called from extract routines */
+    TTMaskSetOnlyType(&defaultSubTypeMask, subType);
+    DBTreeSrTiles(scx, &defaultSubTypeMask, 0, dbEraseSubFunc, (ClientData)&csd);
+
+    /* Next, paint the substrate type in the temporary plane over the	*/
+    /* area of all substrate shield types.				*/
     DBTreeSrTiles(scx, subShieldMask, 0, dbPaintSubFunc, (ClientData)&csd);
     if (csd.csd_modified == FALSE) return NULL;
 
diff --git a/drc/DRCsubcell.c b/drc/DRCsubcell.c
index 34f49223..0d755c38 100644
--- a/drc/DRCsubcell.c
+++ b/drc/DRCsubcell.c
@@ -200,6 +200,10 @@ drcSubCopyFunc(scx, cdarg)
     return DBNoTreeSrTiles(scx, &drcMask, 0, drcSubCopyErrors, cdarg);
 }
 
+/* Flags used by the client data for drcSubcellFunc() */
+#define PROPAGATE_FLAG 1
+#define CELLFOUND_FLAG 2
+
 /*
  * ----------------------------------------------------------------------------
  *
@@ -220,13 +224,16 @@ drcSubCopyFunc(scx, cdarg)
  */
 
 int
-drcSubcellFunc(subUse, propagate)
+drcSubcellFunc(subUse, flags)
     CellUse *subUse;		/* Subcell instance. */
-    bool *propagate;		/* Errors to propagate up */
+    int *flags;			/* Information to propagate up */
 {
     Rect area, haloArea, intArea, subIntArea, locIntArea;
     int i;
 
+    /* A subcell has been seen, so set the "cell found" flag */
+    *flags |= CELLFOUND_FLAG;
+
     /* To determine interactions, find the bounding box of
      * all paint and other subcells within one halo of this
      * subcell (and also within the original area where
@@ -269,7 +276,7 @@ drcSubcellFunc(subUse, propagate)
     GeoInclude(&locIntArea, &intArea);
 #endif
 
-    if (!GEO_RECTNULL(&subIntArea)) *propagate = TRUE;
+    if (!GEO_RECTNULL(&subIntArea)) *flags |= PROPAGATE_FLAG;
 
     drcCurSub = subUse;
     (void) DBSrCellPlaneArea(drcSubDef->cd_cellPlane, &haloArea,
@@ -402,7 +409,7 @@ DRCFindInteractions(def, area, radius, interaction)
     int i;
     CellUse *use;
     SearchContext scx;
-    bool propagate;
+    int flags;
 
     drcSubDef = def;
     drcSubRadius = radius;
@@ -417,9 +424,9 @@ DRCFindInteractions(def, area, radius, interaction)
 
     drcSubIntArea = GeoNullRect;
     GEO_EXPAND(area, radius, &drcSubLookArea);
-    propagate = FALSE;
+    flags = 0;
     (void) DBSrCellPlaneArea(def->cd_cellPlane, &drcSubLookArea,
-		drcSubcellFunc, (ClientData)(&propagate));
+		drcSubcellFunc, (ClientData)(&flags));
 
     /* If there seems to be an interaction area, make a second pass
      * to make sure there's more than one cell with paint in the
@@ -427,13 +434,14 @@ DRCFindInteractions(def, area, radius, interaction)
      * have overlapping bounding boxes without overlapping paint.
      */
 
-    if (GEO_RECTNULL(&drcSubIntArea)) return -1;
+    if (!(flags & CELLFOUND_FLAG)) return -1;
+    if (GEO_RECTNULL(&drcSubIntArea)) return 0;
     use = NULL;
 
     /* If errors are being propagated up from child to parent,	*/
     /* then the interaction area is always valid.		*/
 
-    if (propagate == FALSE)
+    if (!(flags & PROPAGATE_FLAG))
     {
 	for (i = PL_TECHDEPBASE; i < DBNumPlanes; i++)
 	{
diff --git a/extract/ExtBasic.c b/extract/ExtBasic.c
index 115a7ee9..1f1977fd 100644
--- a/extract/ExtBasic.c
+++ b/extract/ExtBasic.c
@@ -3723,6 +3723,14 @@ extFindNodes(def, clipArea, subonly)
 	TTMaskSetMask(&subsTypesNonSpace, &ExtCurStyle->exts_globSubstrateTypes);
 	TTMaskClearType(&subsTypesNonSpace, TT_SPACE);
 
+	/* If the default substrate type is set, it is used *only* for	*/
+	/* isolated substrate regions and does not mark the default	*/
+	/* substrate, so remove it from the list of substrate types.	*/
+
+	if (ExtCurStyle->exts_globSubstrateDefaultType != -1)
+	    TTMaskClearType(&subsTypesNonSpace,
+			ExtCurStyle->exts_globSubstrateDefaultType);
+
 	pNum = ExtCurStyle->exts_globSubstratePlane;
 	/* Does the type set of this plane intersect the substrate types? */
 	if (TTMaskIntersect(&DBPlaneTypes[pNum], &subsTypesNonSpace))
diff --git a/extract/ExtRegion.c b/extract/ExtRegion.c
index 68e4858f..87c43384 100644
--- a/extract/ExtRegion.c
+++ b/extract/ExtRegion.c
@@ -255,66 +255,66 @@ ExtLabelRegions(def, connTo, nodeList, clipArea)
 	}
 	if ((found == FALSE) && (nodeList != NULL))
 	{
-	    /* Unconnected node label.  This may be a "sticky label".
-	     * If it is not connected to TT_SPACE, then create a new
-	     * node region for it.
-	     * (3/24/2015---changed from GEO_LABEL_IN_AREA to GEO_SURROUND)
-	     */
-	    if ((GEO_SURROUND(&lab->lab_rect, clipArea) ||
-			GEO_TOUCH(&lab->lab_rect, clipArea))
-			 && (lab->lab_type != TT_SPACE))
-	    {
-		/* If the label is the substrate type and is over	*/
-		/* space, then assign the label to the default		*/
-		/* substrate region.					*/
+	    /* Handle unconnected node label. */
 
-		if ((pNum == ExtCurStyle->exts_globSubstratePlane) &&
+	    /* If the label is the substrate type and is over	*/
+	    /* space, then assign the label to the default	*/
+	    /* substrate region.  The label need not be in the	*/
+	    /* clip area.					*/
+
+	    if ((pNum == ExtCurStyle->exts_globSubstratePlane) &&
 			TTMaskHasType(&ExtCurStyle->exts_globSubstrateTypes,
 			lab->lab_type))
+	    {
+		if (temp_subsnode != NULL)
 		{
-		    if (glob_subsnode != NULL)
-		    {
-		    	ll = (LabelList *)mallocMagic(sizeof(LabelList));
-		    	ll->ll_label = lab;
-		    	if (lab->lab_flags & PORT_DIR_MASK)
-			    ll->ll_attr = LL_PORTATTR;
-		    	else
-			    ll->ll_attr = LL_NOATTR;
-		    	ll->ll_next = glob_subsnode->nreg_labels;
-		    	glob_subsnode->nreg_labels = ll;
-		    }
-		}
-		else
-		{
-		    NodeRegion *newNode;
-		    int n;
-		    int nclasses;
-
-		    nclasses = ExtCurStyle->exts_numResistClasses;
-	    	    n = sizeof (NodeRegion) + (sizeof (PerimArea) * (nclasses - 1));
-		    newNode = (NodeRegion *)mallocMagic((unsigned) n);
-
 		    ll = (LabelList *)mallocMagic(sizeof(LabelList));
 		    ll->ll_label = lab;
-		    ll->ll_next = NULL;
 		    if (lab->lab_flags & PORT_DIR_MASK)
 			ll->ll_attr = LL_PORTATTR;
 		    else
 			ll->ll_attr = LL_NOATTR;
-
-	 	    newNode->nreg_next = *nodeList;
-		    newNode->nreg_pnum = pNum;
-		    newNode->nreg_type = lab->lab_type;
-		    newNode->nreg_ll = lab->lab_rect.r_ll;
-		    newNode->nreg_cap = (CapValue)0;
-		    newNode->nreg_resist = 0;
-		    for (n = 0; n < nclasses; n++)
-			newNode->nreg_pa[n].pa_perim = newNode->nreg_pa[n].pa_area = 0;
-		    newNode->nreg_labels = ll;
-
-		    *nodeList = newNode;
+		    ll->ll_next = glob_subsnode->nreg_labels;
+		    temp_subsnode->nreg_labels = ll;
 		}
 	    }
+
+	    /* This may be a "sticky label".  If it is not connected to
+	     * TT_SPACE, then create a new node region for it.  The
+	     * label must be within the clip area.
+	     */
+	    else if ((GEO_SURROUND(&lab->lab_rect, clipArea) ||
+			GEO_TOUCH(&lab->lab_rect, clipArea))
+			 && (lab->lab_type != TT_SPACE))
+	    {
+		NodeRegion *newNode;
+		int n;
+		int nclasses;
+
+		nclasses = ExtCurStyle->exts_numResistClasses;
+	    	n = sizeof (NodeRegion) + (sizeof (PerimArea) * (nclasses - 1));
+		newNode = (NodeRegion *)mallocMagic((unsigned) n);
+
+		ll = (LabelList *)mallocMagic(sizeof(LabelList));
+		ll->ll_label = lab;
+		ll->ll_next = NULL;
+		if (lab->lab_flags & PORT_DIR_MASK)
+		    ll->ll_attr = LL_PORTATTR;
+		else
+		    ll->ll_attr = LL_NOATTR;
+
+	 	newNode->nreg_next = *nodeList;
+		newNode->nreg_pnum = pNum;
+		newNode->nreg_type = lab->lab_type;
+		newNode->nreg_ll = lab->lab_rect.r_ll;
+		newNode->nreg_cap = (CapValue)0;
+		newNode->nreg_resist = 0;
+		for (n = 0; n < nclasses; n++)
+		    newNode->nreg_pa[n].pa_perim = newNode->nreg_pa[n].pa_area = 0;
+		newNode->nreg_labels = ll;
+
+		*nodeList = newNode;
+	    }
 	}
     }
 }