diff --git a/database/DBundo.c b/database/DBundo.c
index 255c3af8..84c9a172 100644
--- a/database/DBundo.c
+++ b/database/DBundo.c
@@ -788,9 +788,11 @@ dbUndoCellBack(up)
 	    break;
         case UNDO_CELL_PLACE:
 	    use = findUse(up, TRUE);
-	    DBUnLinkCell(use, up->cue_parent);
-	    DBDeleteCell(use);
-	    (void) DBCellDeleteUse(use);
+	    if(use) {
+		DBUnLinkCell(use, up->cue_parent);
+		DBDeleteCell(use);
+		(void) DBCellDeleteUse(use);
+	    }
 	    DBReComputeBbox(up->cue_parent);
 	    DBWAreaChanged(up->cue_parent, &up->cue_bbox, DBW_ALLWINDOWS,
 		(TileTypeBitMask *) NULL);
@@ -804,9 +806,11 @@ dbUndoCellBack(up)
 	 */
         case UNDO_CELL_CLRID:
 	    use = findUse(up, FALSE);	/* Find it with a NULL id */
-	    (void) DBReLinkCell(use, up->cue_id);
-	    DBWAreaChanged(up->cue_parent, &up->cue_bbox,
-		(int) ~use->cu_expandMask, &DBAllButSpaceBits);
+	    if(use) {
+		(void) DBReLinkCell(use, up->cue_id);
+		DBWAreaChanged(up->cue_parent, &up->cue_bbox,
+			(int) ~use->cu_expandMask, &DBAllButSpaceBits);
+	    }
 	    break;
 	/*
 	 * The following is a hack.
@@ -817,16 +821,20 @@ dbUndoCellBack(up)
 	 */
 	case UNDO_CELL_SETID:
 	    use = findUse(up, TRUE);	/* Find it with current id */
-	    DBUnLinkCell(use, up->cue_parent);
-	    freeMagic(use->cu_id);
-	    use->cu_id = (char *) NULL;
+	    if(use) {
+		DBUnLinkCell(use, up->cue_parent);
+		freeMagic(use->cu_id);
+		use->cu_id = (char *) NULL;
+	    }
 	    break;
 
 	case UNDO_CELL_LOCKDOWN:
 	    use = findUse(up, TRUE);
-	    use->cu_flags = up->cue_flags;
-	    DBWAreaChanged(up->cue_parent, &up->cue_bbox,
+	    if(use) {
+		use->cu_flags = up->cue_flags;
+		DBWAreaChanged(up->cue_parent, &up->cue_bbox,
 			(int) ~use->cu_expandMask, &DBAllButSpaceBits);
+	    }
 	    break;
     }
 }