diff --git a/include/wx/mac/setup0.h b/include/wx/mac/setup0.h
index f0fcaa873d..7d868578b9 100644
--- a/include/wx/mac/setup0.h
+++ b/include/wx/mac/setup0.h
@@ -47,13 +47,14 @@
 // Recommended setting: 0 (please update your code)
 #define WXWIN_COMPATIBILITY_2_4 1
 
-// Set to 0 for accurate dialog units, else 1 to be as per 2.1.16 and before.
-// If migrating between versions, your dialogs may seem to shrink.
+// MSW-only: Set to 0 for accurate dialog units, else 1 for old behaviour when
+// default system font is used for wxWindow::GetCharWidth/Height() instead of
+// the current font.
 //
-// Default is 1
+// Default is 0
 //
-// Recommended setting: 0 (the new calculations are more correct!)
-#define wxDIALOG_UNIT_COMPATIBILITY   1
+// Recommended setting: 0
+#define wxDIALOG_UNIT_COMPATIBILITY   0
 
 // ----------------------------------------------------------------------------
 // debugging settings
diff --git a/include/wx/msw/setup0.h b/include/wx/msw/setup0.h
index c681818534..bcfbb6457a 100644
--- a/include/wx/msw/setup0.h
+++ b/include/wx/msw/setup0.h
@@ -46,13 +46,14 @@
 // Recommended setting: 0 (please update your code)
 #define WXWIN_COMPATIBILITY_2_4 1
 
-// Set to 0 for accurate dialog units, else 1 to be as per 2.1.16 and before.
-// If migrating between versions, your dialogs may seem to shrink.
+// MSW-only: Set to 0 for accurate dialog units, else 1 for old behaviour when
+// default system font is used for wxWindow::GetCharWidth/Height() instead of
+// the current font.
 //
-// Default is 1
+// Default is 0
 //
-// Recommended setting: 0 (the new calculations are more correct!)
-#define wxDIALOG_UNIT_COMPATIBILITY   1
+// Recommended setting: 0
+#define wxDIALOG_UNIT_COMPATIBILITY   0
 
 // ----------------------------------------------------------------------------
 // debugging settings
diff --git a/include/wx/setup_inc.h b/include/wx/setup_inc.h
index 980c77d4ae..2ca2b73758 100644
--- a/include/wx/setup_inc.h
+++ b/include/wx/setup_inc.h
@@ -31,13 +31,14 @@
 // Recommended setting: 0 (please update your code)
 #define WXWIN_COMPATIBILITY_2_4 1
 
-// Set to 0 for accurate dialog units, else 1 to be as per 2.1.16 and before.
-// If migrating between versions, your dialogs may seem to shrink.
+// MSW-only: Set to 0 for accurate dialog units, else 1 for old behaviour when
+// default system font is used for wxWindow::GetCharWidth/Height() instead of
+// the current font.
 //
-// Default is 1
+// Default is 0
 //
-// Recommended setting: 0 (the new calculations are more correct!)
-#define wxDIALOG_UNIT_COMPATIBILITY   1
+// Recommended setting: 0
+#define wxDIALOG_UNIT_COMPATIBILITY   0
 
 // ----------------------------------------------------------------------------
 // debugging settings