diff --git a/apps/restconf/restconf_methods.c b/apps/restconf/restconf_methods.c
index 46708588..84289dd4 100644
--- a/apps/restconf/restconf_methods.c
+++ b/apps/restconf/restconf_methods.c
@@ -1269,9 +1269,8 @@ api_operations_post_input(clicon_handle h,
     xml_name_set(xdata, "data");
     /* Here xdata is: 
      * <data><input xmlns="urn:example:clixon">...</input></data>
-     * Validate that exactly only <input> tag 
      */
-#if 0
+#if 1
     if (debug){
 	cbuf *ccc=cbuf_new();
 	if (clicon_xml2cbuf(ccc, xdata, 0, 0) < 0)
@@ -1279,6 +1278,7 @@ api_operations_post_input(clicon_handle h,
 	clicon_debug(1, "%s DATA:%s", __FUNCTION__, cbuf_get(ccc));
     }
 #endif
+    /* Validate that exactly only <input> tag */
     if ((xinput = xml_child_i_type(xdata, 0, CX_ELMNT)) == NULL ||
 	strcmp(xml_name(xinput),"input") != 0 ||
 	xml_child_nr_type(xdata, CX_ELMNT) != 1){
@@ -1356,8 +1356,9 @@ api_operations_post_output(clicon_handle h,
     cxobj     *x;
     cxobj     *xok;
     cbuf      *cbret = NULL;
-    int        ret;
-
+    int        isempty;
+    
+    //    clicon_debug(1, "%s", __FUNCTION__);
     if ((cbret = cbuf_new()) == NULL){
 	clicon_err(OE_UNIX, 0, "cbuf_new");
 	goto done;
@@ -1380,7 +1381,7 @@ api_operations_post_output(clicon_handle h,
     /* 9. Translate to restconf RPC data */
     xml_name_set(xoutput, "output");
     /* xoutput should now look: <output><x xmlns="uri">0</x></output> */
-#if 0
+#if 1
     if (debug){
 	cbuf *ccc=cbuf_new();
 	if (clicon_xml2cbuf(ccc, xoutput, 0, 0) < 0)
@@ -1388,56 +1389,19 @@ api_operations_post_output(clicon_handle h,
 	clicon_debug(1, "%s XOUTPUT:%s", __FUNCTION__, cbuf_get(ccc));
     }
 #endif
-    /* Validate output (in case handlers are wrong) */
-    if (youtput==NULL){
-	/* Special case, no yang output
-	 * RFC 7950 7.14.4
-	 * If the RPC operation invocation succeeded and no output parameters
-	 * are returned, the <rpc-reply> contains a single <ok/> element
-	 * RFC 8040 3.6.2
-	 * If the "rpc" statement has no "output" section, the response message
-	 * MUST NOT include a message-body and MUST send a "204 No Content"
-	 * status-line instead.
-	 */
-	if ((xok = xml_child_i_type(xoutput, 0, CX_ELMNT)) == NULL ||
-	    strcmp(xml_name(xok),"ok") != 0 ||
-	    xml_child_nr_type(xoutput, CX_ELMNT) != 1){
-	    /* Internal error - invalid output from rpc handler */
-	    if (xok){
-		if (netconf_operation_failed_xml(&xerr, "application",
-					"Internal error: Empty RPC reply is not ok") < 0)
-		    goto done;
-	    }
-	    else
-		if (netconf_operation_failed_xml(&xerr, "application",
-						"Internal error: Empty RPC reply should have OK") < 0)
-		    goto done;
-	    if ((xe = xpath_first(xerr, "rpc-error")) == NULL){
-		clicon_err(OE_XML, EINVAL, "rpc-error not found (internal error)");
-		goto done;
-	    }
-	    if (api_return_err(h, r, xe, pretty, use_xml) < 0)
-		goto done;
-	    goto fail;
-	}
-	FCGX_SetExitStatus(204, r->out); /* OK */
-	FCGX_FPrintF(r->out, "Status: 204 No Content\r\n");
-	FCGX_FPrintF(r->out, "\r\n");
-	goto fail;
-    }
-    else{
+
+    /* Sanity check of outgoing XML 
+     * For now, skip outgoing checks.
+     * (1) Does not handle <ok/> properly
+     * (2) Uncertain how validation errors should be logged/handled
+     */
+    if (youtput!=NULL){
 	xml_spec_set(xoutput, youtput); /* needed for xml_spec_populate */
-	if (0){
-	/* Sanity check of outgoing XML 
-	 * For now, skip outgoing checks.
-	 * (1) Does not handle <ok/> properly
-	 * (2) Uncertain how validation errors should be logged/handled
-	 */
+#if 0
 	if (xml_apply(xoutput, CX_ELMNT, xml_spec_populate, yspec) < 0)
 	    goto done;
 	if ((ret = xml_yang_validate_all(xoutput, cbret)) < 0)
 	    goto done;
-
 	if (ret == 1 &&
 	    (ret = xml_yang_validate_add(xoutput, cbret)) < 0)
 	    goto done;
@@ -1452,14 +1416,34 @@ api_operations_post_output(clicon_handle h,
 		goto done;
 	    goto fail;
 	}
-	}
-	/* Clear namespace of parameters */
-	x = NULL;
-	while ((x = xml_child_each(xoutput, x, CX_ELMNT)) != NULL) {
-	    if ((xa = xml_find_type(x, NULL, "xmlns", CX_ATTR)) != NULL)
-		if (xml_purge(xa) < 0)
-		    goto done;
-	}
+#endif
+    }
+    /* Special case, no yang output (single <ok/> - or empty body?)
+     * RFC 7950 7.14.4
+     * If the RPC operation invocation succeeded and no output parameters
+     * are returned, the <rpc-reply> contains a single <ok/> element
+     * RFC 8040 3.6.2
+     * If the "rpc" statement has no "output" section, the response message
+     * MUST NOT include a message-body and MUST send a "204 No Content"
+     * status-line instead.
+     */
+    isempty = xml_child_nr_type(xoutput, CX_ELMNT) == 0 ||
+	(xml_child_nr_type(xoutput, CX_ELMNT) == 1 &&
+	 (xok = xml_child_i_type(xoutput, 0, CX_ELMNT)) != NULL &&
+	 strcmp(xml_name(xok),"ok")==0);
+    if (isempty) {
+	/* Internal error - invalid output from rpc handler */
+	FCGX_SetExitStatus(204, r->out); /* OK */
+	FCGX_FPrintF(r->out, "Status: 204 No Content\r\n");
+	FCGX_FPrintF(r->out, "\r\n");
+	goto fail;
+    }
+    /* Clear namespace of parameters */
+    x = NULL;
+    while ((x = xml_child_each(xoutput, x, CX_ELMNT)) != NULL) {
+	if ((xa = xml_find_type(x, NULL, "xmlns", CX_ATTR)) != NULL)
+	    if (xml_purge(xa) < 0)
+		goto done;
     }
     /* Set namespace on output */
     if (xmlns_set(xoutput, NULL, namespace) < 0)
@@ -1643,7 +1627,7 @@ api_operations_post(clicon_handle h,
     }
     /* Here xtop is: 
       <rpc username="foo"><myfn xmlns="uri"><x>42</x></myfn></rpc> */
-#if 0
+#if 1
     if (debug){
 	cbuf *ccc=cbuf_new();
 	if (clicon_xml2cbuf(ccc, xtop, 0, 0) < 0)
@@ -1652,8 +1636,8 @@ api_operations_post(clicon_handle h,
 		     __FUNCTION__, cbuf_get(ccc));
     }
 #endif
-    /* 6. Validate outgoing RPC and fill in defaults */
-    if (xml_spec_populate_rpc(h, xtop, yspec) < 0)
+    /* 6. Validate incoming RPC and fill in defaults */
+    if (xml_spec_populate_rpc(h, xtop, yspec) < 0) /*  */
 	goto done;
     if ((ret = xml_yang_validate_rpc(xtop, cbret)) < 0)
 	goto done;
@@ -1710,7 +1694,7 @@ api_operations_post(clicon_handle h,
     /* 8. Receive reply from local/backend handler as Netconf RPC
      *       <rpc-reply><x xmlns="uri">0</x></rpc-reply>
      */
-#if 0
+#if 1
     if (debug){
 	cbuf *ccc=cbuf_new();
 	if (clicon_xml2cbuf(ccc, xret, 0, 0) < 0)
diff --git a/example/clixon-example@2019-01-13.yang b/example/clixon-example@2019-01-13.yang
index 40e53cc6..c664a0ab 100644
--- a/example/clixon-example@2019-01-13.yang
+++ b/example/clixon-example@2019-01-13.yang
@@ -76,7 +76,20 @@ module clixon-example {
 	}
     }
     rpc empty {
-	description "Smallest possible RPC with no input or output";
+	description "Smallest possible RPC with no input or output sections";
+    }
+    rpc optional {
+	description "Small RPC with optional input and output";
+	input {
+	    leaf x {
+		type string;
+	    }
+	}
+	output {
+	    leaf x {
+		type string;
+	    }
+	}
     }
     rpc example {
 	description "Some example input/output for testing RFC7950 7.14.
diff --git a/example/example_backend.c b/example/example_backend.c
index 615d7937..e0adc3ff 100644
--- a/example/example_backend.c
+++ b/example/example_backend.c
@@ -156,19 +156,20 @@ example_rpc(clicon_handle h,            /* Clicon handle */
 	goto done;
     }
     cprintf(cbret, "<rpc-reply>");
-    while ((x = xml_child_each(xe, x, CX_ELMNT)) != NULL) {
-	if (xmlns_set(x, NULL, namespace) < 0)
-	    goto done;
-	if (clicon_xml2cbuf(cbret, x, 0, 0) < 0)
-	    goto done;
-    }
+    if (!xml_child_nr_type(xe, CX_ELMNT))
+	cprintf(cbret, "<ok/>");
+    else while ((x = xml_child_each(xe, x, CX_ELMNT)) != NULL) {
+	    if (xmlns_set(x, NULL, namespace) < 0)
+		goto done;
+	    if (clicon_xml2cbuf(cbret, x, 0, 0) < 0)
+		goto done;
+	}
     cprintf(cbret, "</rpc-reply>");
     retval = 0;
  done:
     return retval;
 }
 
-
 /*! Called to get state data from plugin
  * @param[in]    h      Clicon handle
  * @param[in]    xpath  String with XPATH syntax. or NULL for all
@@ -338,6 +339,12 @@ clixon_plugin_init(clicon_handle h)
 			      "empty"/* Xml tag when callback is made */
 			      ) < 0)
 	goto done;
+    /* Same as example but with optional input/output */
+    if (rpc_callback_register(h, example_rpc, 
+			      NULL, 
+			      "optional"/* Xml tag when callback is made */
+			      ) < 0)
+	goto done;
     if (rpc_callback_register(h, example_rpc, 
 			      NULL, 
 			      "example"/* Xml tag when callback is made */
@@ -349,4 +356,3 @@ clixon_plugin_init(clicon_handle h)
  done:
     return NULL;
 }
-
diff --git a/test/test_restconf.sh b/test/test_restconf.sh
index d0aabca5..6f41f6f7 100755
--- a/test/test_restconf.sh
+++ b/test/test_restconf.sh
@@ -30,27 +30,6 @@ cat <<EOF > $cfg
 </config>
 EOF
 
-cat <<EOF > $fyang
-module mymod{
-    yang-version 1.1;
-    namespace "urn:example:my";
-    prefix me;
-    import clixon-example {
-	prefix ex;
-    }
-    import ietf-interfaces {
-	prefix if;
-    }
-    import ietf-ip {
-      prefix ip;
-    }
-    import ietf-inet-types {
-       prefix "inet";
-       revision-date "2013-07-15";
-    }
-}
-EOF
-
 # This is a fixed 'state' implemented in routing_backend. It is assumed to be always there
 state='{"clixon-example:state": {"op": "42"}}'
 
@@ -94,12 +73,12 @@ expecteq "$(curl -s -H 'Accept: application/yang-data+xml' -G http://localhost/r
 
 # Should be alphabetically ordered
 new2 "restconf get restconf/operations. RFC8040 3.3.2 (json)"
-expecteq "$(curl -sG http://localhost/restconf/operations)" '{"operations": {"clixon-example:client-rpc": null,"clixon-example:empty": null,"clixon-example:example": null,"clixon-lib:debug": null}
+expecteq "$(curl -sG http://localhost/restconf/operations)" '{"operations": {"clixon-example:client-rpc": null,"clixon-example:empty": null,"clixon-example:optional": null,"clixon-example:example": null,"clixon-lib:debug": null}
 
'
 
 new "restconf get restconf/operations. RFC8040 3.3.2 (xml)"
 ret=$(curl -s -H "Accept: application/yang-data+xml" -G http://localhost/restconf/operations)
-expect='<operations><client-rpc xmlns="urn:example:clixon"/><empty xmlns="urn:example:clixon"/><example xmlns="urn:example:clixon"/><debug xmlns="http://clicon.org/lib"/></operations>'
+expect='<operations><client-rpc xmlns="urn:example:clixon"/><empty xmlns="urn:example:clixon"/><optional xmlns="urn:example:clixon"/><example xmlns="urn:example:clixon"/><debug xmlns="http://clicon.org/lib"/></operations>'
 match=`echo $ret | grep -EZo "$expect"`
 if [ -z "$match" ]; then
     err "$expect" "$ret"
@@ -275,7 +254,7 @@ new2 "restconf rpc using wrong prefix"
 expecteq "$(curl -s -X POST -d '{"wrong:input":{"routing-instance-name":"ipv4"}}' http://localhost/restconf/operations/wrong:example)" '{"ietf-restconf:errors" : {"error": {"error-type": "protocol","error-tag": "operation-failed","error-severity": "error","error-message": "yang module not found"}}}
'
 
 new "restconf local client rpc using POST xml"
-ret=$(curl -s -X POST -H "Accept: application/yang-data+xml" -d '{"clixon-example:input":{"request":"example"}}' http://localhost/restconf/operations/clixon-example:client-rpc)
+ret=$(curl -s -i -X POST -H "Accept: application/yang-data+xml" -d '{"clixon-example:input":{"request":"example"}}' http://localhost/restconf/operations/clixon-example:client-rpc)
 expect='<output xmlns="urn:example:clixon"><result>ok</result></output>'
 match=`echo $ret | grep -EZo "$expect"`
 if [ -z "$match" ]; then
diff --git a/test/test_rpc.sh b/test/test_rpc.sh
index 464a0fc5..076ced83 100755
--- a/test/test_rpc.sh
+++ b/test/test_rpc.sh
@@ -2,6 +2,9 @@
 # RPC tests
 # Validate parameters in restconf and netconf, check namespaces, etc
 # See rfc8040 3.6
+# Use the example application that has one mandatory input arg,
+# At the end is an alternative Yang without mandatory arg for
+# valid empty input and output.
 APPNAME=example
 
 # include err() and new() functions and creates $dir
@@ -95,7 +98,7 @@ expecteof "$clixon_netconf -qf $cfg" 0 '<rpc xmlns="urn:ietf:params:xml:ns:netco
 
 # 2. Then error cases
 #
-new "restconf empy rpc with null input"
+new "restconf empty rpc with null input"
 ret=$(curl -is -X POST -d '{"clixon-example:input":null}' http://localhost/restconf/operations/clixon-example:empty)
 expect="204 No Content"
 match=`echo $ret | grep -EZo "$expect"`
@@ -103,9 +106,18 @@ if [ -z "$match" ]; then
     err "$expect" "$ret"
 fi
 
-new2 "restconf empy rpc with input x"
+new2 "restconf empty rpc with input x"
 expecteq "$(curl -s -X POST -d '{"clixon-example:input":{"x":0}}' http://localhost/restconf/operations/clixon-example:empty)" '{"ietf-restconf:errors" : {"error": {"error-type": "application","error-tag": "unknown-element","error-info": {"bad-element": "x"},"error-severity": "error"}}}
'
 
+# cornercase: optional has yang input/output sections but test without body
+new "restconf optional rpc with null input and output"
+ret=$(curl -is -X POST -d '{"clixon-example:input":null}' http://localhost/restconf/operations/clixon-example:optional)
+expect="204 No Content"
+match=`echo $ret | grep -EZo "$expect"`
+if [ -z "$match" ]; then
+    err "$expect" "$ret"
+fi
+
 new2 "restconf omit mandatory"
 expecteq "$(curl -s -X POST -d '{"clixon-example:input":null}' http://localhost/restconf/operations/clixon-example:example)" '{"ietf-restconf:errors" : {"error": {"error-type": "application","error-tag": "missing-element","error-info": {"bad-element": "x"},"error-severity": "error","error-message": "Mandatory variable"}}}
'
 
@@ -118,7 +130,6 @@ expecteq "$(curl -s -X POST -d '{"clixon-example:input":{"x":"0"}}' http://local
 new2 "restconf example missing input"
 expecteq "$(curl -s -X POST -d '{"clixon-example:input":null}' http://localhost/restconf/operations/ietf-netconf:edit-config)" '{"ietf-restconf:errors" : {"error": {"error-type": "protocol","error-tag": "operation-failed","error-severity": "error","error-message": "yang module not found"}}}
'
 
-
 new "netconf kill-session missing session-id mandatory"
 expecteof "$clixon_netconf -qf $cfg" 0 '<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"><kill-session/></rpc>]]>]]>' '^<rpc-reply><rpc-error><error-type>application</error-type><error-tag>missing-element</error-tag><error-info><bad-element>session-id</bad-element></error-info><error-severity>error</error-severity><error-message>Mandatory variable</error-message></rpc-error></rpc-reply>]]>]]>$'