diff --git a/src/cli.c b/src/cli.c
index 694372d..d2c97ae 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -124,6 +124,9 @@ int scan_args_validate(scan_args_t *args, int argc, const char **argv) {
         args->tn_count = DEFAULT_THUMBNAIL_COUNT;
     } else if (args->tn_count == OPTION_VALUE_DISABLE) {
         args->tn_count = 0;
+    } else if (args->tn_count > 1000) {
+        printf("Invalid value --thumbnail-count argument: %d. Must be <= 1000.\n", args->tn_size);
+        return 1;
     }
 
     if (args->content_size == OPTION_VALUE_UNSPECIFIED) {