Index: layer_grp.c
===================================================================
--- layer_grp.c	(revision 31858)
+++ layer_grp.c	(revision 31859)
@@ -821,11 +821,17 @@
 				/* finalize group */
 				if (loc & PCB_LYT_INTERN) {
 					g = pcb_get_grp_new_intern(pcb, -1);
-					assert(g != NULL);
+					if (g == NULL) {
+						rnd_message(RND_MSG_ERROR, "pcb_layer_parse_group_string(): unable to insert layer groups for copper\n");
+						goto error;
+					}
 				}
 				else {
 					g = pcb_get_grp(LayerGroup, loc, PCB_LYT_COPPER);
-					assert(g != NULL);
+					if (g == NULL) {
+						rnd_message(RND_MSG_ERROR, "pcb_layer_parse_group_string(): unable to insert layer groups for copper\n");
+						goto error;
+					}
 				}
 
 				for(n = 0; n < lids_len; n++) {