diff --git a/tools/ei-demo-client.c b/tools/ei-demo-client.c
index b12de52..16ce9a0 100644
--- a/tools/ei-demo-client.c
+++ b/tools/ei-demo-client.c
@@ -258,10 +258,16 @@ main(int argc, char **argv)
 			receiver = true;
 			break;
 		case OPT_INTERVAL:
-			interval = atoi(optarg);
+			if (!xatou(optarg, &interval)) {
+				fprintf(stderr, "Invalid interval: %s\n", optarg);
+				return EXIT_FAILURE;
+			}
 			break;
 		case OPT_ITERATIONS:
-			iterations = atoi(optarg);
+			if (!xatou(optarg, &iterations)) {
+				fprintf(stderr, "Invalid iterations: %s\n", optarg);
+				return EXIT_FAILURE;
+			}
 			break;
 		default:
 			usage(stderr, argv[0]);
diff --git a/tools/eis-demo-server.c b/tools/eis-demo-server.c
index 9cf04ad..06a9c89 100644
--- a/tools/eis-demo-server.c
+++ b/tools/eis-demo-server.c
@@ -698,7 +698,10 @@ main(int argc, char **argv)
 			verbose = true;
 			break;
 		case OPT_INTERVAL:
-			interval = atoi(optarg);
+			if (!xatou(optarg, &interval)) {
+				fprintf(stderr, "Invalid interval: %s\n", optarg);
+				return EXIT_FAILURE;
+			}
 			break;
 		default:
 			usage(stderr, argv[0]);