diff --git a/CHANGES b/CHANGES
index 24461aa88..56fa5e126 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,5 +1,6 @@
 CHANGES IN FLTK 1.3.3                                              RELEASED: MMM DD YYYY
 
+	- fix crash if Fl_Window::flush() was called, but window not shown() (STR #3028).
 	- new method Fl::scheme_is(const char *name) returns 1 if current scheme is name.
 	- Fixed recent MinGW build WRT configure not finding strcasecmp() (STR #2994).
 	  Note: This fix is temporary and should be revisited later.
diff --git a/src/Fl.cxx b/src/Fl.cxx
index fcb16555d..1916052ce 100644
--- a/src/Fl.cxx
+++ b/src/Fl.cxx
@@ -1750,6 +1750,7 @@ void Fl_Widget::damage(uchar fl, int X, int Y, int W, int H) {
   Fl::damage(FL_DAMAGE_CHILD);
 }
 void Fl_Window::flush() {
+  if (!shown()) return;
   make_current();
 //if (damage() == FL_DAMAGE_EXPOSE && can_boxcheat(box())) fl_boxcheat = this;
   fl_clip_region(i->region); i->region = 0;
diff --git a/src/Fl_Double_Window.cxx b/src/Fl_Double_Window.cxx
index 943e065af..fb93c9cd9 100644
--- a/src/Fl_Double_Window.cxx
+++ b/src/Fl_Double_Window.cxx
@@ -369,6 +369,7 @@ void Fl_Double_Window::flush() {flush(0);}
   and leaving the clip region set to the entire window.
 */
 void Fl_Double_Window::flush(int eraseoverlay) {
+  if (!shown()) return;
   make_current(); // make sure fl_gc is non-zero
   Fl_X *myi = Fl_X::i(this);
   if (!myi) return; // window not yet created
diff --git a/src/Fl_Gl_Window.cxx b/src/Fl_Gl_Window.cxx
index f5b41a2a0..9c29a7b38 100644
--- a/src/Fl_Gl_Window.cxx
+++ b/src/Fl_Gl_Window.cxx
@@ -292,6 +292,7 @@ int fl_overlay_depth = 0;
 
 
 void Fl_Gl_Window::flush() {
+  if (!shown()) return;
   uchar save_valid = valid_f_ & 1;
 #if HAVE_GL_OVERLAY && defined(WIN32)
   uchar save_valid_f = valid_f_;
diff --git a/src/Fl_Menu_Window.cxx b/src/Fl_Menu_Window.cxx
index 28e121d0a..02bee699e 100644
--- a/src/Fl_Menu_Window.cxx
+++ b/src/Fl_Menu_Window.cxx
@@ -54,6 +54,7 @@ void Fl_Menu_Window::show() {
 }
 
 void Fl_Menu_Window::flush() {
+  if (!shown()) return;
 #if HAVE_OVERLAY
   if (!fl_overlay_visual || !overlay()) {Fl_Single_Window::flush(); return;}
   Fl_X *myi = Fl_X::i(this);
diff --git a/src/Fl_x.cxx b/src/Fl_x.cxx
index e1831b5c4..22acff7e9 100644
--- a/src/Fl_x.cxx
+++ b/src/Fl_x.cxx
@@ -34,6 +34,7 @@
 #  include <FL/Fl_Tooltip.H>
 #  include <FL/fl_draw.H>
 #  include <FL/Fl_Paged_Device.H>
+#  include <FL/fl_ask.H>
 #  include <stdio.h>
 #  include <stdlib.h>
 #  include "flstring.h"
@@ -2339,6 +2340,10 @@ GC fl_gc;
 // make X drawing go into this window (called by subclass flush() impl.)
 void Fl_Window::make_current() {
   static GC gc; // the GC used by all X windows
+  if (!shown()) {
+    fl_alert("Fl_Window::make_current(), but window is not shown().");
+    Fl::fatal("Fl_Window::make_current(), but window is not shown().");
+  }
   if (!gc) gc = XCreateGC(fl_display, i->xid, 0, 0);
   fl_window = i->xid;
   fl_gc = gc;