1 files changed, 9 insertions, 2 deletions
diff --git a/packages/gitbook-core/src/reducers/navigation.js b/packages/gitbook-core/src/reducers/navigation.js
index 9831cd5..439ba21 100644
--- a/packages/gitbook-core/src/reducers/navigation.js
+++ b/packages/gitbook-core/src/reducers/navigation.js
@@ -1,11 +1,13 @@
-const { Record } = require('immutable');
+const { Record, List } = require('immutable');
 const ACTION_TYPES = require('../actions/TYPES');
 
 const NavigationState = Record({
     // Are we loading a new page
     loading: Boolean(false),
     // Did we fail loading a page?
-    error:   null
+    error:   null,
+    // Listener for history changes
+    listeners: List()
 });
 
 function reduceNavigation(state, action) {
@@ -28,6 +30,11 @@ function reduceNavigation(state, action) {
             error:   action.error
         });
 
+    case ACTION_TYPES.NAVIGATION_LISTEN:
+        return state.merge({
+            listeners: state.listeners.push(action.listener)
+        });
+
     default:
         return state;