diff --git a/tools/export_evblob.c b/tools/export_evblob.c
index 34b6ef5..7124e1d 100644
--- a/tools/export_evblob.c
+++ b/tools/export_evblob.c
@@ -79,13 +79,16 @@ return 0;
 /*			EXPERIMENTAL GRUIK-CODE !!!			 */
 int printf_the_edges(EdgesAndVertices *eav)
 {
-int		idx, a, b;
+int		idx, a, b, vmax;
 
 #if DEBUG_LEVEL
 fprintf(stderr, ">>> %s ( %p )\n", __func__, eav);
 #endif
 
-if (verbosity) fprintf(stderr, "fprinting %d edges\n", eav->Elist->fidx);
+if (verbosity) fprintf(stderr, "    fprinting %d edges\n", eav->Elist->fidx);
+
+vmax = eav->Blist->fidx;
+fprintf(stderr, "    in %s, vmax was %d\n", __func__, vmax);
 
 /*
  *	OK we have (maybe) all the data in da place
@@ -95,7 +98,12 @@ for (idx=0; idx<eav->Elist->fidx; idx++) {
 
 	a = eav->Elist->edges[idx].A;
 	b = eav->Elist->edges[idx].B;
-	// fprintf(stderr, "%7d %7d\n", a, b);
+
+	/* this is a Molly-Guard */
+	if ( (a<0) || (b<0) || (a>vmax) || (b>vmax) ) {
+		fprintf(stderr, "ERROR: vmax=%d a=%d b=%d\n", vmax, a, b);
+		return -1;
+		}
 
 	printf("%.9f %.9f %.9f   %.9f %.9f %.9f\n",
 		eav->Blist->bbs[a].p.x,
@@ -142,25 +150,34 @@ else if (! strcasecmp("bbox",     outmode)) { mode = 2; }
 
 switch (mode) {
 	case 0:
-		printf_the_edges(&eav);			break;
+		foo = printf_the_edges(&eav);			break;
 	case 1:
-		printf_the_vertices(&eav);		break;
+		foo = printf_the_vertices(&eav);		break;
 	case 2:
-		printf_the_boudingbox(&eav);		break;
+		foo = printf_the_boudingbox(&eav);		break;
 
 	default:
-		fprintf(stderr, "no way to do '%s'\n", outmode);
+		fprintf(stderr, "%s: no way for '%s'\n", __func__, outmode);
 		exit(1);
 		break;
 	}
 
+if (foo) {
+	fprintf(stderr, "%s: action '%s' -> %d\n", __func__, outmode, foo);
+	exit(1);
+	}
+
 return 0;
 }
 /* --------------------------------------------------------------------- */
 void help(void)
 {
-fprintf(stderr, "YOLO!\n");
-/* XXX */
+
+puts("usage:\n  $ export_evblob [opts] fichier.evblob");
+puts("\t-h\tsome short help...");
+puts("\t-t\tone of [edges vertices bbox]");
+puts("\t-v\tbe more verbose");
+
 exit(0);
 }
 /* --------------------------------------------------------------------- */