diff -urN qt-everywhere-opensource-src-4.8.1.orig/src/tools/moc/main.cpp qt-everywhere-opensource-src-4.8.1/src/tools/moc/main.cpp
--- qt-everywhere-opensource-src-4.8.1.orig/src/tools/moc/main.cpp	2012-05-04 18:45:34.122912347 +0200
+++ qt-everywhere-opensource-src-4.8.1/src/tools/moc/main.cpp	2012-05-04 18:51:28.267484929 +0200
@@ -187,6 +187,7 @@
     Moc moc;
     pp.macros["Q_MOC_RUN"];
     pp.macros["__cplusplus"];
+    pp.macros["BOOST_TT_HAS_OPERATOR_HPP_INCLUDED"]; // Gentoo bug #401551
     QByteArray filename;
     QByteArray output;
     FILE *in = 0;