diff --git a/source3/winbindd/winbindd_cache.c b/source3/winbindd/winbindd_cache.c
index 370475a90aa..0ca683e8d9d 100644
--- a/source3/winbindd/winbindd_cache.c
+++ b/source3/winbindd/winbindd_cache.c
@@ -1241,7 +1241,8 @@ NTSTATUS wcache_cached_creds_exist(struct winbindd_domain *domain, const struct
 {
 	struct winbind_cache *cache = get_cache(domain);
 	int ret;
-	fstring key_str, tmp;
+	struct dom_sid_buf tmp;
+	fstring key_str;
 	uint32_t rid;
 
 	if (!cache->tdb) {
@@ -1256,7 +1257,7 @@ NTSTATUS wcache_cached_creds_exist(struct winbindd_domain *domain, const struct
 		return NT_STATUS_INVALID_SID;
 	}
 
-	fstr_sprintf(key_str, "CRED/%s", sid_to_fstring(tmp, sid));
+	fstr_sprintf(key_str, "CRED/%s", dom_sid_str_buf(sid, &tmp));
 
 	ret = tdb_exists(cache->tdb, string_tdb_data(key_str));
 	if (ret != 1) {
@@ -1279,7 +1280,7 @@ NTSTATUS wcache_get_creds(struct winbindd_domain *domain,
 	struct cache_entry *centry = NULL;
 	NTSTATUS status;
 	uint32_t rid;
-	fstring tmp;
+	struct dom_sid_buf tmp;
 
 	if (!cache->tdb) {
 		return NT_STATUS_INTERNAL_DB_ERROR;
@@ -1297,7 +1298,7 @@ NTSTATUS wcache_get_creds(struct winbindd_domain *domain,
 	   fall back to an unsalted cred. */
 
 	centry = wcache_fetch(cache, domain, "CRED/%s",
-			      sid_to_fstring(tmp, sid));
+			      dom_sid_str_buf(sid, &tmp));
 	if (!centry) {
 		DEBUG(10,("wcache_get_creds: entry for [CRED/%s] not found\n", 
 			  sid_string_dbg(sid)));
@@ -1318,15 +1319,15 @@ NTSTATUS wcache_get_creds(struct winbindd_domain *domain,
 
 	*cached_nt_pass = (const uint8_t *)centry_hash16(centry, mem_ctx);
 	if (*cached_nt_pass == NULL) {
-		fstring sidstr;
+		struct dom_sid_buf sidstr;
 
-		sid_to_fstring(sidstr, sid);
+		dom_sid_str_buf(sid, &sidstr);
 
 		/* Bad (old) cred cache. Delete and pretend we
 		   don't have it. */
 		DEBUG(0,("wcache_get_creds: bad entry for [CRED/%s] - deleting\n", 
-				sidstr));
-		wcache_delete("CRED/%s", sidstr);
+				sidstr.buf));
+		wcache_delete("CRED/%s", sidstr.buf);
 		centry_free(centry);
 		return NT_STATUS_OBJECT_NAME_NOT_FOUND;
 	}
@@ -1359,7 +1360,7 @@ NTSTATUS wcache_save_creds(struct winbindd_domain *domain,
 			   const uint8_t nt_pass[NT_HASH_LEN])
 {
 	struct cache_entry *centry;
-	fstring sid_string;
+	struct dom_sid_buf sid_str;
 	uint32_t rid;
 	uint8_t cred_salt[NT_HASH_LEN];
 	uint8_t salted_hash[NT_HASH_LEN];
@@ -1387,9 +1388,9 @@ NTSTATUS wcache_save_creds(struct winbindd_domain *domain,
 
 	centry_put_hash16(centry, salted_hash);
 	centry_put_hash16(centry, cred_salt);
-	centry_end(centry, "CRED/%s", sid_to_fstring(sid_string, sid));
+	centry_end(centry, "CRED/%s", dom_sid_str_buf(sid, &sid_str));
 
-	DEBUG(10,("wcache_save_creds: %s\n", sid_string));
+	DEBUG(10,("wcache_save_creds: %s\n", sid_str.buf));
 
 	centry_free(centry);
 
@@ -2450,9 +2451,11 @@ static char *wcache_make_sidlist(TALLOC_CTX *mem_ctx, uint32_t num_sids,
 		return NULL;
 	}
 	for (i=0; i<num_sids; i++) {
-		fstring tmp;
+		struct dom_sid_buf tmp;
 		sidlist = talloc_asprintf_append_buffer(
-			sidlist, "/%s", sid_to_fstring(tmp, &sids[i]));
+			sidlist,
+			"/%s",
+			dom_sid_str_buf(&sids[i], &tmp));
 		if (sidlist == NULL) {
 			return NULL;
 		}
@@ -3423,11 +3426,12 @@ NTSTATUS wcache_remove_oldest_cached_creds(struct winbindd_domain *domain, const
 	/* we possibly already have an entry */
  	if (sid && NT_STATUS_IS_OK(wcache_cached_creds_exist(domain, sid))) {
 
-		fstring key_str, tmp;
+		fstring key_str;
+		struct dom_sid_buf tmp;
 
 		DEBUG(11,("we already have an entry, deleting that\n"));
 
-		fstr_sprintf(key_str, "CRED/%s", sid_to_fstring(tmp, sid));
+		fstr_sprintf(key_str, "CRED/%s", dom_sid_str_buf(sid, &tmp));
 
 		tdb_delete(cache->tdb, string_tdb_data(key_str));
 
@@ -4384,7 +4388,7 @@ static int pack_tdc_domains( struct winbindd_tdc_domain *domains,
 	/* now pack each domain trust record */
 	for ( i=0; i<num_domains; i++ ) {
 
-		fstring tmp;
+		struct dom_sid_buf tmp;
 
 		if ( buflen > 0 ) {
 			DEBUG(10,("pack_tdc_domains: Packing domain %s (%s)\n",
@@ -4395,7 +4399,7 @@ static int pack_tdc_domains( struct winbindd_tdc_domain *domains,
 		len += tdb_pack( buffer+len, buflen-len, "fffddd",
 				 domains[i].domain_name,
 				 domains[i].dns_name ? domains[i].dns_name : "",
-				 sid_to_fstring(tmp, &domains[i].sid),
+				 dom_sid_str_buf(&domains[i].sid, &tmp),
 				 domains[i].trust_flags,
 				 domains[i].trust_attribs,
 				 domains[i].trust_type );