diff --git a/packages/web_ui/src/model/instance.jsx b/packages/web_ui/src/model/instance.jsx
index 5b027d3a..ef4f27a2 100644
--- a/packages/web_ui/src/model/instance.jsx
+++ b/packages/web_ui/src/model/instance.jsx
@@ -10,21 +10,20 @@ export function useInstance(id) {
 	let [instance, setInstance] = useState({ loading: true });
 
 	function updateInstance() {
-		if (!Number.isInteger(id)) {
-			setInstance({ missing: true });
-			return;
-		}
-
 		libLink.messages.getInstance.send(control, { id }).then(result => {
 			setInstance({ ...result, present: true });
 		}).catch(err => {
-			logger.log(`Failed to get instance: ${err}`);
+			logger.error(`Failed to get instance: ${err}`);
 			setInstance({ missing: true });
 		});
 
 	}
 
 	useEffect(() => {
+		if (!Number.isInteger(id)) {
+			setInstance({ missing: true });
+			return undefined;
+		}
 		updateInstance();
 
 		function updateHandler(newInstance) {
diff --git a/packages/web_ui/src/model/slave.jsx b/packages/web_ui/src/model/slave.jsx
index c29e7405..729e671a 100644
--- a/packages/web_ui/src/model/slave.jsx
+++ b/packages/web_ui/src/model/slave.jsx
@@ -9,11 +9,6 @@ export function useSlave(id) {
 	let [slave, setSlave] = useState({ loading: true });
 
 	function updateSlave() {
-		if (!Number.isInteger(id)) {
-			setSlave({ missing: true });
-			return;
-		}
-
 		// XXX optimize by requesting only the slave in question
 		libLink.messages.listSlaves.send(control).then(result => {
 			let match = result.list.find(i => i.id === id);
@@ -26,6 +21,10 @@ export function useSlave(id) {
 	}
 
 	useEffect(() => {
+		if (!Number.isInteger(id)) {
+			setSlave({ missing: true });
+			return undefined;
+		}
 		updateSlave();
 
 		function updateHandler(newSlave) {