diff --git a/src/x509.c b/src/x509.c
index 31d76f6..b0048ec 100644
--- a/src/x509.c
+++ b/src/x509.c
@@ -223,7 +223,7 @@ static int meth_issuer(lua_State* L)
 /**
  * Retrieve the extensions from the certificate.
  */
-int meth_extensions(lua_State* L)
+static int meth_extensions(lua_State* L)
 {
   int j;
   int i = -1;