diff --git a/main.c b/main.c
index 42836b2..bea6c0c 100644
--- a/main.c
+++ b/main.c
@@ -798,7 +798,8 @@ main (int argc, char *argv[])
         for (int i = 0; i < NB_CSS; ++i) {
             if (options & OPT_INLINE_CSS) {
                 css[i].offset = ctx.sa_names.len;
-                if (!openreadfileclose(css[i].file, &ctx.sa_names, 0))
+                if (!openreadfileclose(css[i].file, &ctx.sa_names, 0)
+                        || !stralloc_0(&ctx.sa_names))
                     strerr_diefu3sys(-ERR_IO, "load CSS from '", css[i].file, "'");
             } else {
                 int from, to;