--- /usr/portage/dev-lisp/ecls/ecls-13.5.1-r1.ebuild	2014-08-11 09:01:06.000000000 +1200
+++ ecls-13.5.1-r1.ebuild	2014-08-27 09:35:50.445163962 +1200
@@ -47,6 +47,11 @@
 }
 
 src_configure() {
+	local myeconf
+	if [[ ${ELIBC} == "glibc" ]]; then
+		myeconf=$(use_with threads __thread)
+	fi
+
 	econf \
 		--with-system-gmp \
 		--enable-boehm=system \
@@ -57,10 +62,10 @@
 		$(use_with debug debug-cflags) \
 		$(use_with sse) \
 		$(use_enable threads) \
-		$(use_with threads __thread) \
 		$(use_enable unicode) \
 		$(use_with X x) \
-		$(use_with X clx)
+		$(use_with X clx) \
+		${myeconf}
 }
 
 src_compile() {