diff --git a/acinclude.m4 b/acinclude.m4
index 3f222ab..f78c719 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -1883,7 +1883,7 @@ else
  all_includes="$KDE_INCLUDES $all_includes"
 fi
 
-KDE_DEFAULT_CXXFLAGS="-DQT_NO_ASCII_CAST -DQT_NO_STL -DQT_NO_COMPAT -DQT_NO_TRANSLATION"
+KDE_DEFAULT_CXXFLAGS="-DTQT_NO_ASCII_CAST -DTQT_NO_STL -DTQT_NO_COMPAT -DTQT_NO_TRANSLATION"
  
 KDE_LDFLAGS="-L$kde_libraries"
 if test ! "$kde_libraries" = "$x_libraries" && test ! "$kde_libraries" = "$qt_libraries" ; then 
diff --git a/src/kdiff3.pro b/src/kdiff3.pro
index 71ff682..048037b 100644
--- a/src/kdiff3.pro
+++ b/src/kdiff3.pro
@@ -38,12 +38,12 @@ INCLUDEPATH += . ./kreplacements
 
 win32 {
 #   QMAKE_CXXFLAGS_DEBUG  -= -Zi
-#   QMAKE_CXXFLAGS_DEBUG  += -GX -GR -Z7 /FR -DQT_NO_ASCII_CAST
+#   QMAKE_CXXFLAGS_DEBUG  += -GX -GR -Z7 /FR -DTQT_NO_ASCII_CAST
 #   QMAKE_LFLAGS_DEBUG  += /PDB:NONE
-#   QMAKE_CXXFLAGS_RELEASE  += -GX -GR -DNDEBUG -DQT_NO_ASCII_CAST
+#   QMAKE_CXXFLAGS_RELEASE  += -GX -GR -DNDEBUG -DTQT_NO_ASCII_CAST
 
-   QMAKE_CXXFLAGS_DEBUG  += -DQT_NO_ASCII_CAST
-   QMAKE_CXXFLAGS_RELEASE  += -DNDEBUG -DQT_NO_ASCII_CAST
+   QMAKE_CXXFLAGS_DEBUG  += -DTQT_NO_ASCII_CAST
+   QMAKE_CXXFLAGS_RELEASE  += -DNDEBUG -DTQT_NO_ASCII_CAST
    RC_FILE = kdiff3.rc
 }
 unix {