diff --git a/src/basicauth.c b/src/basicauth.c
index ed0553b8..33d964b0 100644
--- a/src/basicauth.c
+++ b/src/basicauth.c
@@ -35,7 +35,7 @@
 ssize_t basicauth_string(const char *user, const char *pass,
 	char *buf, size_t bufsize)
 {
-	char tmp[256+2];
+	char tmp[bufsize+2];
 	int l;
 	if (!user || !pass) return -1;
 	l = snprintf(tmp, sizeof tmp, "%s:%s", user, pass);
diff --git a/src/upstream.c b/src/upstream.c
index 52dad808..c07f810b 100644
--- a/src/upstream.c
+++ b/src/upstream.c
@@ -78,7 +78,7 @@ static struct upstream *upstream_build (const char *host, int port, char *domain
         up->host = up->ua.user = up->pass = NULL;
         if (user) {
                 if (type == PT_HTTP) {
-                        char b[BASE64ENC_BYTES((256+2)-1) + 1];
+                        char b[BASE64ENC_BYTES((strlen(user)+strlen(pass)+2)-1) + 1];
                         ssize_t ret;
                         ret = basicauth_string(user, pass, b, sizeof b);
                         if (ret == 0) {