1 files changed, 1 insertions, 1 deletions

diff --git a/src/openssl.c b/src/openssl.c
index ab19410..f9ff4d5 100644
--- a/src/openssl.c
+++ b/src/openssl.c
@@ -4537,7 +4537,7 @@ static int sx_setAlpnProtos(lua_State *L) {
                                 return luaL_argerror(L, 2, "array of strings expected");
                 }
                 tmp = luaL_checklstring(L, -1, &len);
-                luaL_argcheck(L, len <= UCHAR_MAX, 2, "proto string too long");
+                luaL_argcheck(L, len > 0 && len <= UCHAR_MAX, 2, "proto string length invalid");
                 luaL_addchar(&B, (unsigned char)len);
                 luaL_addlstring(&B, tmp, len);
                 lua_pop(L, 1);