diff --git a/src/corelib/serialization/qcborcommon.h b/src/corelib/serialization/qcborcommon.h
index 202bc49278d..4c52e8bfa48 100644
--- a/src/corelib/serialization/qcborcommon.h
+++ b/src/corelib/serialization/qcborcommon.h
@@ -118,11 +118,4 @@ QT_END_NAMESPACE
 
 QT_DECL_METATYPE_EXTERN(QCborTag, Q_CORE_EXPORT)
 
-// To avoid changing namespace we need to reinstate defines, even though our .cpp
-// will then have to remove them again.
-#if defined(QT_X11_DEFINES_FOUND)
-#  define True  1
-#  define False 0
-#endif
-
 #endif // QCBORSTREAM_H
diff --git a/src/corelib/serialization/qcborstreamreader.h b/src/corelib/serialization/qcborstreamreader.h
index 5c03f95f0c2..12de39f78f9 100644
--- a/src/corelib/serialization/qcborstreamreader.h
+++ b/src/corelib/serialization/qcborstreamreader.h
@@ -203,9 +203,4 @@ private:
 
 QT_END_NAMESPACE
 
-#if defined(QT_X11_DEFINES_FOUND)
-#  define True  1
-#  define False 0
-#endif
-
 #endif // QCBORSTREAMREADER_H
diff --git a/src/corelib/serialization/qcborstreamwriter.h b/src/corelib/serialization/qcborstreamwriter.h
index 630cf67b7a4..976a0cb34a4 100644
--- a/src/corelib/serialization/qcborstreamwriter.h
+++ b/src/corelib/serialization/qcborstreamwriter.h
@@ -88,9 +88,4 @@ private:
 
 QT_END_NAMESPACE
 
-#if defined(QT_X11_DEFINES_FOUND)
-#  define True  1
-#  define False 0
-#endif
-
 #endif // QCBORSTREAMWRITER_H
diff --git a/src/corelib/serialization/qcborvalue.h b/src/corelib/serialization/qcborvalue.h
index 4f4349bee33..ca477e3d44e 100644
--- a/src/corelib/serialization/qcborvalue.h
+++ b/src/corelib/serialization/qcborvalue.h
@@ -620,9 +620,4 @@ Q_CORE_EXPORT QDataStream &operator>>(QDataStream &, QCborValue &);
 
 QT_END_NAMESPACE
 
-#if defined(QT_X11_DEFINES_FOUND)
-#  define True  1
-#  define False 0
-#endif
-
 #endif // QCBORVALUE_H