diff --git a/CHANGES b/CHANGES
index 2ee8429d5..f17166b28 100644
--- a/CHANGES
+++ b/CHANGES
@@ -103,6 +103,9 @@ CHANGES IN FLTK 1.3.4					RELEASED: ??? ?? 2016
 
 	Bug fixes
 
+	- Fix potential crash if Fl_Window::icon(NULL) was called to clear
+	  (reset) a window icon. This is now legal and documented behavior.
+	  The same applies to Fl_Window::default_icon().
 	- Allow widget callback to be NULL, i.e. no callback (STR #2835).
 	- Fixed Fl_Help_View buffer overflow (STR #3275).
 	- Fl_Browser now correctly adjusts its scrollbars when the default
diff --git a/src/Fl_Window.cxx b/src/Fl_Window.cxx
index ffc7f9f87..b066efe61 100644
--- a/src/Fl_Window.cxx
+++ b/src/Fl_Window.cxx
@@ -295,14 +295,19 @@ const char *Fl_Window::xclass() const
 
 /** Sets a single default window icon.
 
-  \param[in] icon default icon for all windows subsequently created
+  If \p icon is NULL the current default icons are removed.
+
+  \param[in] icon default icon for all windows subsequently created or NULL
 
   \see Fl_Window::default_icons(const Fl_RGB_Image *[], int)
   \see Fl_Window::icon(const Fl_RGB_Image *)
   \see Fl_Window::icons(const Fl_RGB_Image *[], int)
  */
 void Fl_Window::default_icon(const Fl_RGB_Image *icon) {
-  default_icons(&icon, 1);
+  if (icon)
+    default_icons(&icon, 1);
+  else
+    default_icons(&icon, 0);
 }
 
 /** Sets the default window icons.
@@ -316,7 +321,7 @@ void Fl_Window::default_icon(const Fl_RGB_Image *icon) {
   variable or free the images immediately after this call.
 
   \param[in] icons default icons for all windows subsequently created
-  \param[in] count number of images in \p icons. set to 0 to remove
+  \param[in] count number of images in \p icons. Set to 0 to remove
                    the current default icons
 
   \see Fl_Window::default_icon(const Fl_RGB_Image *)
@@ -327,25 +332,45 @@ void Fl_Window::default_icons(const Fl_RGB_Image *icons[], int count) {
   Fl_X::set_default_icons(icons, count);
 }
 
-/** Sets a single window icon.
+/** Sets or resets a single window icon.
 
-  \param[in] icon icon for this window
+  A window icon \e can be changed while the window is shown, but this
+  \e may be platform and/or window manager dependent. To be sure that
+  the window displays the correct window icon you should always set the
+  icon before the window is shown.
+
+  If a window icon has not been set for a particular window, then the
+  default window icon (see links below) or the system default icon will
+  be used.
+
+  \param[in] icon icon for this window, NULL to reset window icon.
 
   \see Fl_Window::default_icon(const Fl_RGB_Image *)
   \see Fl_Window::default_icons(const Fl_RGB_Image *[], int)
   \see Fl_Window::icons(const Fl_RGB_Image *[], int)
  */
 void Fl_Window::icon(const Fl_RGB_Image *icon) {
-  icons(&icon, 1);
+  if (icon)
+    icons(&icon, 1);
+  else
+    icons(&icon, 0);
 }
 
 /** Sets the window icons.
 
+  You may set multiple window icons with different sizes. Dependent on
+  the platform and system settings the best (or the first) icon will be
+  chosen.
+
   The given images in \p icons are copied. You can use a local
   variable or free the images immediately after this call.
 
+  If \p count is zero, current icons are removed. If \p count is greater than
+  zero (must not be negative), then \p icons[] must contain at least \p count
+  valid image pointers (not NULL). Otherwise the behavior is undefined.
+
   \param[in] icons icons for this window
-  \param[in] count number of images in \p icons. set to 0 to remove
+  \param[in] count number of images in \p icons. Set to 0 to remove
                    the current icons
 
   \see Fl_Window::default_icon(const Fl_RGB_Image *)
diff --git a/src/Fl_x.cxx b/src/Fl_x.cxx
index 165d0a8b9..e0be1a0a6 100644
--- a/src/Fl_x.cxx
+++ b/src/Fl_x.cxx
@@ -2702,6 +2702,8 @@ void Fl_Window::size_range_() {
 static unsigned long *default_net_wm_icons = 0L;
 static size_t default_net_wm_icons_size = 0;
 
+// Note: icons[] *must* contain at least <count> valid image pointers (!NULL),
+//  but: <count> *may* be 0
 static void icons_to_property(const Fl_RGB_Image *icons[], int count,
                               unsigned long **property, size_t *len) {
   size_t sz;