diff --git a/tests/libtest/lib678.c b/tests/libtest/lib678.c
index 73aa4ee7e9..7486505f76 100644
--- a/tests/libtest/lib678.c
+++ b/tests/libtest/lib678.c
@@ -97,7 +97,7 @@ static CURLcode test_lib678(const char *URL)
   curl_global_init(CURL_GLOBAL_DEFAULT);
   if(!strcmp("check", URL)) {
     CURLcode w = CURLE_OK;
-    struct curl_blob blob = { 0 };
+    struct curl_blob blob = { CURL_UNCONST("silly"), 5, 0 };
     CURL *curl = curl_easy_init();
     if(curl) {
       w = curl_easy_setopt(curl, CURLOPT_CAINFO_BLOB, &blob);