diff --git a/CHANGELOG.md b/CHANGELOG.md
index cfc98c42..8a0ddc86 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,7 +12,7 @@
   * Get it with `clicon_nsctx_global_get(h)`
 * Added wildcard `*` as a mode to `CLICON_MODE` in clispec files
   * If you set "CLICON_MODE="*";" in a clispec file it means that syntax will appear in all CLI spec modes.
-* State callbacks provided by user are validated. If they are invalid an internal error is returned.
+* State callbacks provided by user are validated. If they are invalid an internal error is returned, example, with error-tag: `operation-failed`and with error-message containing. `Internal error, state callback returned invalid XML`.
 * Fixed multi-namespace for augmented state which was not covered in 4.2.0.
 
 ### API changes on existing features (you may need to change your code)
diff --git a/apps/backend/backend_plugin.c b/apps/backend/backend_plugin.c
index 6ca91325..1dde1a65 100644
--- a/apps/backend/backend_plugin.c
+++ b/apps/backend/backend_plugin.c
@@ -134,19 +134,25 @@ clixon_plugin_statedata(clicon_handle    h,
 	if (ret > 0 && (ret = xml_yang_validate_add(h, x, &xerr)) < 0)
 	    goto done;
 	if (ret == 0){
-	    if ((cberr = cbuf_new()) ==NULL){
-		clicon_err(OE_XML, errno, "cbuf_new");
-		goto done;
+	    cxobj *xe;
+	    cxobj *xb;
+	    
+	    if ((xe = xpath_first(xerr, NULL, "//error-tag")) != NULL &&
+		(xb = xml_body_get(xe))){
+		if (xml_value_set(xb, "operation-failed") < 0)
+		    goto done;
+	    }
+	    if ((xe = xpath_first(xerr, NULL, "//error-message")) != NULL &&
+		(xb = xml_body_get(xe))){
+		if (xml_value_append(xb, " Internal error, state callback returned invalid XML") < 0)
+		    goto done;
 	    }
-	    cprintf(cberr, "Internal error: state callback returned invalid XML: ");
-	    if (netconf_err2cb(xpath_first(xerr, NULL, "rpc-error"), cberr) < 0)
-		goto done;
 	    if (*xret){
 		xml_free(*xret);
 		*xret = NULL;
 	    }
-	    if (netconf_operation_failed_xml(xret, "application", cbuf_get(cberr))< 0)
-		goto done;
+	    *xret = xerr;
+	    xerr = NULL;
 	    goto fail;
 	}
 #if 1
diff --git a/lib/src/clixon_netconf_lib.c b/lib/src/clixon_netconf_lib.c
index 54b9072d..040d65eb 100644
--- a/lib/src/clixon_netconf_lib.c
+++ b/lib/src/clixon_netconf_lib.c
@@ -953,7 +953,7 @@ netconf_operation_not_supported(cbuf *cb,
  * some reason not covered by any other error condition.
  * @param[out] cb      CLIgen buf. Error XML is written in this buffer
  * @param[in]  type    Error type: "rpc", "application" or "protocol"
- * @param[in]  message Error message
+ * @param[in]  message Error message (will be XML encoded)
  * @see netconf_operation_failed_xml  Same but returns XML tree
  */
 int
@@ -994,6 +994,7 @@ int
 netconf_operation_failed_xml(cxobj **xret,
 			     char  *type,
 			     char  *message)
+
 {
     int   retval =-1;
     cxobj *xerr;
@@ -1009,7 +1010,8 @@ netconf_operation_failed_xml(cxobj **xret,
 	goto done;
     if (xml_parse_va(&xerr, NULL, "<error-type>%s</error-type>"
 		     "<error-tag>operation-failed</error-tag>"
-		     "<error-severity>error</error-severity>", type) < 0)
+		     "<error-severity>error</error-severity>",
+		     type) < 0)
 	goto done;
     if (message){
 	 if (xml_chardata_encode(&encstr, "%s", message) < 0)
diff --git a/lib/src/clixon_xml_map.c b/lib/src/clixon_xml_map.c
index 2caaea91..63daa827 100644
--- a/lib/src/clixon_xml_map.c
+++ b/lib/src/clixon_xml_map.c
@@ -1274,13 +1274,27 @@ xml_yang_validate_all(clicon_handle h,
     int        nr;
     int        ret;
     cxobj     *x;
+    char      *namespace = NULL;
+    cbuf      *cb = NULL;
 
     /* if not given by argument (overide) use default link 
        and !Node has a config sub-statement and it is false */
     ys=xml_spec(xt);
     if (ys==NULL){
-	if (netconf_unknown_element_xml(xret, "application", xml_name(xt), NULL) < 0)
+	if ((cb = cbuf_new()) == NULL){
+	    clicon_err(OE_UNIX, errno, "cbuf_new");
 	    goto done;
+	}
+	if (xml2ns(xt, xml_prefix(xt), &namespace) < 0)
+	    goto done;
+	if (namespace){
+	    cprintf(cb, "namespace is: %s", namespace);
+	    if (netconf_unknown_element_xml(xret, "application", xml_name(xt), cbuf_get(cb)) < 0)
+		goto done;
+	}
+	else
+	    if (netconf_unknown_element_xml(xret, "application", xml_name(xt), NULL) < 0)
+		goto done;
 	goto fail;
     }
     if (yang_config(ys) != 0){
@@ -1326,7 +1340,7 @@ xml_yang_validate_all(clicon_handle h,
 		goto done;
 	    if (!nr){
 		ye = yang_find(yc, Y_ERROR_MESSAGE, NULL);
-		if (netconf_operation_failed_xml(xret, "application",
+		if (netconf_operation_failed_xml(xret, "application", 
 					     ye?ye->ys_argument:"must xpath validation failed") < 0)
 		    goto done;
 		goto fail;
@@ -1338,7 +1352,7 @@ xml_yang_validate_all(clicon_handle h,
 	    if ((nr = xpath_vec_bool(xt, NULL, "%s", xpath)) < 0)
 		goto done;
 	    if (!nr){
-		if (netconf_operation_failed_xml(xret, "application",
+		if (netconf_operation_failed_xml(xret, "application", 
 					     "when xpath validation failed") < 0)
 		    goto done;
 		goto fail;
@@ -1363,6 +1377,8 @@ xml_yang_validate_all(clicon_handle h,
  ok:
     retval = 1;
  done:
+    if (cb)
+	cbuf_free(cb);
     return retval;
  fail:
     retval = 0;