diff --git a/lib/cf-https-connect.c b/lib/cf-https-connect.c
index 1d50fba103..f324d5d2c3 100644
--- a/lib/cf-https-connect.c
+++ b/lib/cf-https-connect.c
@@ -350,7 +350,7 @@ static CURLcode cf_hc_resolv(struct Curl_cfilter *cf,
         rr->port == cf->conn->remote_port)) {
       for(i = 0; i < CURL_ARRAYSIZE(rr->alpns) &&
                  alpn_count < CURL_ARRAYSIZE(alpn_ids); ++i) {
-        enum alpnid alpn = rr->alpns[i];
+        enum alpnid alpn = (enum alpnid)rr->alpns[i];
         if(cf_https_alpns_contain(alpn, alpn_ids, alpn_count))
           continue;
         switch(alpn) {