diff --git a/win/Qt/qt_bind.cpp b/win/Qt/qt_bind.cpp
index d1c007e4e..047368ac2 100644
--- a/win/Qt/qt_bind.cpp
+++ b/win/Qt/qt_bind.cpp
@@ -7,7 +7,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_click.cpp b/win/Qt/qt_click.cpp
index a72d62a16..d8f5030b7 100644
--- a/win/Qt/qt_click.cpp
+++ b/win/Qt/qt_click.cpp
@@ -7,7 +7,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_delay.cpp b/win/Qt/qt_delay.cpp
index 7a510f506..0fa3003ce 100644
--- a/win/Qt/qt_delay.cpp
+++ b/win/Qt/qt_delay.cpp
@@ -7,7 +7,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_glyph.cpp b/win/Qt/qt_glyph.cpp
index 5a7336252..6c1df7c0c 100644
--- a/win/Qt/qt_glyph.cpp
+++ b/win/Qt/qt_glyph.cpp
@@ -8,7 +8,6 @@ extern "C" {
 #include "hack.h"
 #include "tile2x11.h" /* x11tiles is potential fallback for nhtiles.bmp */
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_icon.cpp b/win/Qt/qt_icon.cpp
index 46057c804..fea574742 100644
--- a/win/Qt/qt_icon.cpp
+++ b/win/Qt/qt_icon.cpp
@@ -27,7 +27,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_inv.cpp b/win/Qt/qt_inv.cpp
index ec8077f4f..50f17f47c 100644
--- a/win/Qt/qt_inv.cpp
+++ b/win/Qt/qt_inv.cpp
@@ -21,7 +21,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_key.cpp b/win/Qt/qt_key.cpp
index 2f2d13b70..b598d6b1d 100644
--- a/win/Qt/qt_key.cpp
+++ b/win/Qt/qt_key.cpp
@@ -7,7 +7,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_line.cpp b/win/Qt/qt_line.cpp
index 0482ca25a..482122589 100644
--- a/win/Qt/qt_line.cpp
+++ b/win/Qt/qt_line.cpp
@@ -7,7 +7,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_main.cpp b/win/Qt/qt_main.cpp
index 465d61a3f..59543bd1f 100644
--- a/win/Qt/qt_main.cpp
+++ b/win/Qt/qt_main.cpp
@@ -6,9 +6,8 @@
 
 extern "C" {
 #include "hack.h"
+#define CTRL(c) (0x1f & (c)) // substitute for C() from global.h, for ^V hack
 }
-#undef C
-#define CTRL(c) (0x1f & (c))
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_map.cpp b/win/Qt/qt_map.cpp
index c805e9eea..3eb766866 100644
--- a/win/Qt/qt_map.cpp
+++ b/win/Qt/qt_map.cpp
@@ -7,7 +7,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_menu.cpp b/win/Qt/qt_menu.cpp
index 4425b8a35..202769bfa 100644
--- a/win/Qt/qt_menu.cpp
+++ b/win/Qt/qt_menu.cpp
@@ -28,7 +28,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_msg.cpp b/win/Qt/qt_msg.cpp
index 04ba80b2a..66fd93dae 100644
--- a/win/Qt/qt_msg.cpp
+++ b/win/Qt/qt_msg.cpp
@@ -7,7 +7,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_plsel.cpp b/win/Qt/qt_plsel.cpp
index 2bba646a2..c9fd09756 100644
--- a/win/Qt/qt_plsel.cpp
+++ b/win/Qt/qt_plsel.cpp
@@ -18,7 +18,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_pre.h b/win/Qt/qt_pre.h
index 53f7e4718..980196aeb 100644
--- a/win/Qt/qt_pre.h
+++ b/win/Qt/qt_pre.h
@@ -6,6 +6,7 @@
  * #include after "hack.h", before <Qt.../Qt...>.
  */
 
+#undef C            // conflicts with Qt6 header
 #undef Invisible
 #undef Warning
 #undef index
diff --git a/win/Qt/qt_rip.cpp b/win/Qt/qt_rip.cpp
index 91bf1ad25..b4aeb1a3a 100644
--- a/win/Qt/qt_rip.cpp
+++ b/win/Qt/qt_rip.cpp
@@ -7,7 +7,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_set.cpp b/win/Qt/qt_set.cpp
index 5f9328653..2f6655417 100644
--- a/win/Qt/qt_set.cpp
+++ b/win/Qt/qt_set.cpp
@@ -8,7 +8,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_stat.cpp b/win/Qt/qt_stat.cpp
index 81b8f5d9f..5fce613c6 100644
--- a/win/Qt/qt_stat.cpp
+++ b/win/Qt/qt_stat.cpp
@@ -78,7 +78,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_streq.cpp b/win/Qt/qt_streq.cpp
index c98ef5dbb..dc6712a4d 100644
--- a/win/Qt/qt_streq.cpp
+++ b/win/Qt/qt_streq.cpp
@@ -7,7 +7,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_svsel.cpp b/win/Qt/qt_svsel.cpp
index a1509d4e6..9fcc3854d 100644
--- a/win/Qt/qt_svsel.cpp
+++ b/win/Qt/qt_svsel.cpp
@@ -41,7 +41,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_win.cpp b/win/Qt/qt_win.cpp
index 06ebf62a8..b957a2282 100644
--- a/win/Qt/qt_win.cpp
+++ b/win/Qt/qt_win.cpp
@@ -49,7 +49,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_xcmd.cpp b/win/Qt/qt_xcmd.cpp
index 50b724f83..f1c203903 100644
--- a/win/Qt/qt_xcmd.cpp
+++ b/win/Qt/qt_xcmd.cpp
@@ -77,7 +77,6 @@ extern "C" {
 #include "hack.h"
 #include "func_tab.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>
diff --git a/win/Qt/qt_yndlg.cpp b/win/Qt/qt_yndlg.cpp
index c2f28505c..89b132eb3 100644
--- a/win/Qt/qt_yndlg.cpp
+++ b/win/Qt/qt_yndlg.cpp
@@ -7,7 +7,6 @@
 extern "C" {
 #include "hack.h"
 }
-#undef C
 
 #include "qt_pre.h"
 #include <QtGui/QtGui>