diff --git a/browser/base/content/tabbrowser.xml b/browser/base/content/tabbrowser.xml
index 57b412ef4839..57c54ca7f2f9 100644
--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -1494,6 +1494,9 @@
 
             let wasActive = document.activeElement == aBrowser;
 
+            // Unmap the old outerWindowID.
+            this._outerWindowIDBrowserMap.delete(aBrowser.outerWindowID);
+
             // Unhook our progress listener.
             let tab = this.getTabForBrowser(aBrowser);
             let index = tab._tPos;
@@ -1525,6 +1528,9 @@
               tab.removeAttribute("crashed");
             } else {
               aBrowser.messageManager.sendAsyncMessage("Browser:AppTab", { isAppTab: tab.pinned })
+
+              // Register the new outerWindowID.
+              this._outerWindowIDBrowserMap.set(aBrowser.outerWindowID, aBrowser);
             }
 
             if (wasActive)