diff --git a/libraries/fltk/src/Fl_Text_Buffer.cxx b/libraries/fltk/src/Fl_Text_Buffer.cxx
index f26afb39d..b9806a7ac 100644
--- a/libraries/fltk/src/Fl_Text_Buffer.cxx
+++ b/libraries/fltk/src/Fl_Text_Buffer.cxx
@@ -14,6 +14,7 @@
 //     https://www.fltk.org/bugs.php
 //
 
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <FL/fl_utf8.h>
diff --git a/libraries/fltk/src/drivers/GDI/Fl_GDI_Graphics_Driver_image.cxx b/libraries/fltk/src/drivers/GDI/Fl_GDI_Graphics_Driver_image.cxx
index 3a8e70689..6182c8e68 100644
--- a/libraries/fltk/src/drivers/GDI/Fl_GDI_Graphics_Driver_image.cxx
+++ b/libraries/fltk/src/drivers/GDI/Fl_GDI_Graphics_Driver_image.cxx
@@ -34,6 +34,7 @@
 ////////////////////////////////////////////////////////////////
 
 #include <config.h>
+#include <stdint.h>
 #include "Fl_GDI_Graphics_Driver.H"
 #include "../WinAPI/Fl_WinAPI_System_Driver.H"
 #include <FL/Fl.H>
diff --git a/libraries/fltk/src/drivers/Xlib/Fl_Xlib_Graphics_Driver_image.cxx b/libraries/fltk/src/drivers/Xlib/Fl_Xlib_Graphics_Driver_image.cxx
index 5dafe503f..7ff980cb6 100644
--- a/libraries/fltk/src/drivers/Xlib/Fl_Xlib_Graphics_Driver_image.cxx
+++ b/libraries/fltk/src/drivers/Xlib/Fl_Xlib_Graphics_Driver_image.cxx
@@ -44,6 +44,7 @@
 ////////////////////////////////////////////////////////////////
 
 #include <config.h>
+#include <stdint.h>
 #include "Fl_Xlib_Graphics_Driver.H"
 #include "../X11/Fl_X11_Screen_Driver.H"
 #include "../X11/Fl_X11_Window_Driver.H"