diff --git a/library/x509_create.c b/library/x509_create.c
index d7a1fee..d3d5851 100644
--- a/library/x509_create.c
+++ b/library/x509_create.c
@@ -36,7 +36,7 @@
     int ret = 0;
     char *s = name, *c = s;
     char *end = s + strlen( s );
-    char *oid = NULL;
+    const char *oid = NULL;
     int in_tag = 1;
     asn1_named_data *cur;