diff -Naur Terminal-0.9.9.orig/TerminalWindow.h Terminal-0.9.9/TerminalWindow.h
--- Terminal-0.9.9.orig/TerminalWindow.h	2016-06-10 19:50:22.000000000 +0200
+++ Terminal-0.9.9/TerminalWindow.h	2020-09-16 18:31:15.680833836 +0200
@@ -17,7 +17,7 @@
 #import <AppKit/NSWindowController.h>
 #import <AppKit/NSTabView.h>
 
-NSString *TerminalWindowNoMoreActiveWindowsNotification;
+extern NSString *TerminalWindowNoMoreActiveWindowsNotification;
 
 @interface TerminalWindowController : NSWindowController
 {