diff --git a/client/app/scripts/actions/app-actions.js b/client/app/scripts/actions/app-actions.js
index 1cd740407..03350c590 100644
--- a/client/app/scripts/actions/app-actions.js
+++ b/client/app/scripts/actions/app-actions.js
@@ -405,7 +405,8 @@ export function clickTopology(topologyId) {
 export function cacheZoomState(zoomState) {
   return {
     type: ActionTypes.CACHE_ZOOM_STATE,
-    zoomState
+    // Make sure only proper numerical values are cached.
+    zoomState: zoomState.filter(value => !window.isNaN(value)),
   };
 }
 
diff --git a/client/app/scripts/reducers/root.js b/client/app/scripts/reducers/root.js
index 9bbe144f1..1cfafc5bf 100644
--- a/client/app/scripts/reducers/root.js
+++ b/client/app/scripts/reducers/root.js
@@ -88,7 +88,8 @@ export const initialState = makeMap({
   topologyViewMode: GRAPH_VIEW_MODE,
   version: '...',
   versionUpdate: null,
-  viewport: makeMap(),
+  // Set some initial numerical values to prevent NaN in case of edgy race conditions.
+  viewport: makeMap({ width: 0, height: 0 }),
   websocketClosed: false,
   zoomCache: makeMap(),
   serviceImages: makeMap()