diff --git a/lib/src/clixon_datastore_write.c b/lib/src/clixon_datastore_write.c
index 12879c6d..2875b40a 100644
--- a/lib/src/clixon_datastore_write.c
+++ b/lib/src/clixon_datastore_write.c
@@ -191,6 +191,8 @@ check_body_namespace(cxobj     *x0,
     cxobj     *x;
     int        isroot;
     cbuf      *cberr = NULL;
+    yang_stmt *yspec = NULL;
+    yang_stmt *yns = NULL;
 
     /* XXX: need to identify root better than hiereustics and strcmp,... */
     isroot = xml_parent(x0p)==NULL &&
@@ -240,7 +242,21 @@ check_body_namespace(cxobj     *x0,
     else if (ns0 == NULL && ns1 != NULL){ /* namespace exists in x1 but not in x0: OK (but request is realy invalid */
     }
 #endif
-    else{ /* Namespace does not exist in x0: error */
+    else{ /* Namespace does not exist in x0 or x1: try YANG, else error */
+        if (y && (yspec = ys_spec(y)) != NULL &&
+            (yns = yang_find_module_by_prefix_yspec(yspec, prefix)) != NULL &&
+            (ns0 = yang_find_mynamespace(yns)) != NULL){
+            if (isroot)
+                x = x0;
+            else
+                x = x0p;
+            if (nscache_set(x, prefix, ns0) < 0)
+                goto done;
+            if (xml_add_attr(x, prefix, ns0, "xmlns", NULL) == NULL)
+                goto done;
+            xml_sort(x);
+            goto ok;
+        }
         if ((cberr = cbuf_new()) == NULL){
             clixon_err(OE_UNIX, errno, "cbuf_new");
             goto done;
diff --git a/test/test_openconfig_spanning_tree_enabled_protocol.sh b/test/test_openconfig_spanning_tree_enabled_protocol.sh
new file mode 100644
index 00000000..0a73ff8b
--- /dev/null
+++ b/test/test_openconfig_spanning_tree_enabled_protocol.sh
@@ -0,0 +1,69 @@
+#!/usr/bin/env bash
+# Verify openconfig-spanning-tree enabled-protocol identityref resolves oc-stp-types prefix.
+# Reproduces CLI error: "prefix \"oc-stp-types\" has no associated namespace"
+
+# Magic line must be first in script (see README.md)
+s="$_"
+. ./lib.sh || if [ "$s" = $0 ]; then exit 0; else return 0; fi
+
+APPNAME=example
+
+new "openconfig"
+if [ ! -d "$OPENCONFIG" ]; then
+    #    err "Hmm Openconfig dir does not seem to exist, try git clone https://github.com/openconfig/public?"
+    echo "...skipped: OPENCONFIG not set"
+    rm -rf $dir
+    if [ "$s" = $0 ]; then exit 0; else return 0; fi
+fi
+
+OCSTP=$OPENCONFIG/release/models/stp/openconfig-spanning-tree.yang
+cfg=$dir/openconfig_spanning_tree_enabled_protocol.xml
+
+AUTOCLI=$(autocli_config "*" kw-nokey false)
+
+cat <<EOF >$cfg
+<clixon-config xmlns="http://clicon.org/config">
+  <CLICON_CONFIGFILE>$cfg</CLICON_CONFIGFILE>
+  <CLICON_YANG_DIR>${OPENCONFIG}</CLICON_YANG_DIR>
+  <CLICON_YANG_DIR>${YANG_INSTALLDIR}</CLICON_YANG_DIR>
+  <CLICON_YANG_MAIN_FILE>$OCSTP</CLICON_YANG_MAIN_FILE>
+  <CLICON_YANG_AUGMENT_ACCEPT_BROKEN>true</CLICON_YANG_AUGMENT_ACCEPT_BROKEN>
+  <CLICON_CLISPEC_DIR>/usr/local/lib/$APPNAME/clispec</CLICON_CLISPEC_DIR>
+  <CLICON_CLI_DIR>/usr/local/lib/$APPNAME/cli</CLICON_CLI_DIR>
+  <CLICON_CLI_MODE>$APPNAME</CLICON_CLI_MODE>
+  <CLICON_SOCK>/usr/local/var/run/$APPNAME.sock</CLICON_SOCK>
+  <CLICON_BACKEND_PIDFILE>/usr/local/var/run/$APPNAME.pidfile</CLICON_BACKEND_PIDFILE>
+  <CLICON_XMLDB_DIR>$dir</CLICON_XMLDB_DIR>
+  $AUTOCLI
+</clixon-config>
+EOF
+
+if [ $BE -ne 0 ]; then
+    new "kill old backend"
+    sudo clixon_backend -zf $cfg
+    new "start backend -s init -f $cfg"
+    start_backend -s init -f $cfg
+fi
+
+new "wait backend"
+wait_backend
+
+new "cli set stp global enabled-protocol identityref"
+expectpart "$($clixon_cli -1 -f $cfg set stp global config enabled-protocol oc-stp-types:MSTP 2>&1)" 0 "^$"
+
+new "discard-changes"
+expecteof_netconf "$clixon_netconf -qf $cfg" 0 "$DEFAULTHELLO" "<rpc $DEFAULTNS><discard-changes/></rpc>" "" "<rpc-reply $DEFAULTNS><ok/></rpc-reply>"
+
+if [ $BE -ne 0 ]; then
+    new "Kill backend"
+    pid=$(pgrep -u root -f clixon_backend)
+    if [ -z "$pid" ]; then
+        err "backend already dead"
+    fi
+    stop_backend -f $cfg
+fi
+
+rm -rf $dir
+
+new "endtest"
+endtest