diff --git a/lib/vtls/openssl.c b/lib/vtls/openssl.c
index fc0c1c35f5..98fa962ab0 100644
--- a/lib/vtls/openssl.c
+++ b/lib/vtls/openssl.c
@@ -3968,7 +3968,7 @@ CURLcode Curl_ossl_ctx_init(struct ossl_ctx *octx,
 # endif
           else {
             trying_ech_now = 1;
-            infof(data, "ECH: imported ECHConfigList of length %ld", elen);
+            infof(data, "ECH: imported ECHConfigList of length %zu", elen);
           }
         }
         else {