diff --git a/src/boe.menus.win.cpp b/src/boe.menus.win.cpp
index d568bb59..b0937da3 100644
--- a/src/boe.menus.win.cpp
+++ b/src/boe.menus.win.cpp
@@ -14,7 +14,7 @@
 
 // Include this last because some #defines in the Windows headers cause compile errors in my headers.
 // Fortunately they're on symbols not used in this file, so this should work.
-#include <Windows.h>
+#include <windows.h>
 #include <gl/GL.h>
 #undef HELP_INDEX // Except this one
 
diff --git a/src/pcedit/pc.menus.win.cpp b/src/pcedit/pc.menus.win.cpp
index c5244985..4d57c492 100644
--- a/src/pcedit/pc.menus.win.cpp
+++ b/src/pcedit/pc.menus.win.cpp
@@ -9,7 +9,7 @@
 
 // Include this last because some #defines in the Windows headers cause compile errors in my headers.
 // Fortunately they're on symbols not used in this file, so this should work.
-#include <Windows.h>
+#include <windows.h>
 
 // This is the index of each menu on the menubar
 enum {
diff --git a/src/scenedit/scen.menus.win.cpp b/src/scenedit/scen.menus.win.cpp
index 5708477d..80fb6153 100644
--- a/src/scenedit/scen.menus.win.cpp
+++ b/src/scenedit/scen.menus.win.cpp
@@ -9,7 +9,7 @@
 
 // Include this last because some #defines in the Windows headers cause compile errors in my headers.
 // Fortunately they're on symbols not used in this file, so this should work.
-#include <Windows.h>
+#include <windows.h>
 #undef HELP_INDEX // Except this one.
 
 // This is the index of each menu on the menubar
diff --git a/src/tools/cursors.win.cpp b/src/tools/cursors.win.cpp
index 0fedd709..4aadfc16 100644
--- a/src/tools/cursors.win.cpp
+++ b/src/tools/cursors.win.cpp
@@ -1,6 +1,6 @@
 
 #include "cursors.hpp"
-#include <Windows.h>
+#include <windows.h>
 #include <exception>
 #include <SFML/Graphics/RenderWindow.hpp>
 #include "restypes.hpp"
diff --git a/src/tools/debugout.win.cpp b/src/tools/debugout.win.cpp
index 1e741e4e..126f1c78 100644
--- a/src/tools/debugout.win.cpp
+++ b/src/tools/debugout.win.cpp
@@ -1,7 +1,7 @@
 
 #include <sstream>
 #include <iostream>
-#include <Windows.h>
+#include <windows.h>
 
 // Debugger streambuf adapted from here: <http://www.codeproject.com/Articles/1053/Using-an-output-stream-for-debugging>
 
diff --git a/src/tools/graphtool.cpp b/src/tools/graphtool.cpp
index a7c2b9af..28aa5dbe 100644
--- a/src/tools/graphtool.cpp
+++ b/src/tools/graphtool.cpp
@@ -13,7 +13,7 @@
 #include <OpenGl/GL.h>
 #else
 #ifdef _WIN32
-#include <Windows.h>
+#include <windows.h>
 #endif
 #include <GL/GL.h>
 #endif
diff --git a/src/tools/menu_accel.win.hpp b/src/tools/menu_accel.win.hpp
index 742773b2..ada12c8c 100644
--- a/src/tools/menu_accel.win.hpp
+++ b/src/tools/menu_accel.win.hpp
@@ -1,5 +1,5 @@
 
-#include <Windows.h>
+#include <windows.h>
 #include <vector>
 
 struct accel_table_t {
diff --git a/src/tools/winutil.win.cpp b/src/tools/winutil.win.cpp
index 6c434ff1..8994b267 100644
--- a/src/tools/winutil.win.cpp
+++ b/src/tools/winutil.win.cpp
@@ -1,7 +1,7 @@
 
 #include "winutil.hpp"
 #include <iostream>
-#include <Windows.h>
+#include <windows.h>
 #include <SFML/Graphics/RenderWindow.hpp>
 #include <SFML/Graphics/Image.hpp>
 #include <sstream>