1 files changed, 10 insertions, 2 deletions

diff --git a/src/openssl.c b/src/openssl.c
index 900b909..9ea9469 100644
--- a/src/openssl.c
+++ b/src/openssl.c
@@ -4989,9 +4989,13 @@ static int xe_new(lua_State *L) {
         lua_settop(L, 3);
         ud = prepsimple(L, X509_EXT_CLASS);
 
-        if (!lua_isnil(L, 3)) {
+        switch (lua_type(L, 3)) {
+        case LUA_TNONE:
+        case LUA_TNIL:
+                break;
+        case LUA_TSTRING: {
                 size_t len;
-                const char *cdata = luaL_checklstring(L, 3, &len);
+                const char *cdata = lua_tolstring(L, 3, &len);
                 _Bool crit;
 
                 if (xe_new_isder(value, &crit)) {
@@ -5015,6 +5019,10 @@ static int xe_new(lua_State *L) {
 
                 ctx = &cbuf;
                 X509V3_set_nconf(ctx, conf);
+                break;
+        }
+        default:
+                return luaL_argerror(L, 3, "invalid extra parameter (expected string or nil)");
         }
 
         /*