--- /usr/portage/dev-lang/tcl/tcl-8.5.9.ebuild	2011-08-05 10:31:08.000000000 +0200
+++ tcl-8.5.9.ebuild	2011-08-12 18:56:48.000000000 +0200
@@ -49,6 +49,10 @@
 	if use hppa; then
 		append-cflags "-DTCL_NO_STACK_CHECK=1"
 	fi
+	# a real hack
+	if [[ ( "${ABI}" == "x86" ) && ( "${DEFAULT_ABI}" == "amd64" ) ]]; then
+		append-cflags "-DTCL_NO_STACK_CHECK=1"
+	fi
 
 	tc-export CC