diff --git a/CHANGES b/CHANGES
index 0d0822c68..35b81b382 100644
--- a/CHANGES
+++ b/CHANGES
@@ -146,6 +146,7 @@ CHANGES IN FLTK 1.3.0
 
 	  Bug Fixes
 
+	- Fixed potential crash in fl_xid() on Linux (STR #2635)
 	- Fixed keyboard navigation in fl_choice() (STR #2591)
 	- Fixed alpha blending under X11 when line data size != 0 (STR #2606)
 	- Fixed Fl_Tabs selection border drawing, if tabs are at the bottom
diff --git a/FL/x.H b/FL/x.H
index b9be0343b..1a7a4625c 100644
--- a/FL/x.H
+++ b/FL/x.H
@@ -174,7 +174,7 @@ public:
 extern FL_EXPORT char fl_override_redirect; // hack into Fl_X::make_xid()
 extern FL_EXPORT int fl_background_pixel;  // hack into Fl_X::make_xid()
 
-inline Window fl_xid(const Fl_Window* w) { return Fl_X::i(w)->xid; }
+inline Window fl_xid(const Fl_Window* w) { Fl_X *temp = Fl_X::i(w); return temp ? temp->xid : 0; }
 
 #else
 
diff --git a/src/Fl_x.cxx b/src/Fl_x.cxx
index 913c7200d..95aff3d3e 100644
--- a/src/Fl_x.cxx
+++ b/src/Fl_x.cxx
@@ -1902,12 +1902,11 @@ void Fl_Window::make_current() {
 #endif
 }
 
-Window fl_xid_(const Fl_Window* w)
-{
-  return Fl_X::i(w)->xid;
+Window fl_xid_(const Fl_Window *w) {
+  Fl_X *temp = Fl_X::i(w);
+  return temp ? temp->xid : 0;
 }
 
-
 int Fl_Window::decorated_h()
 {
   if (parent() || !shown()) return h();