diff --git a/GNUmakefile.in b/GNUmakefile.in
index d5adf4d5..68896340 100644
--- a/GNUmakefile.in
+++ b/GNUmakefile.in
@@ -48,10 +48,6 @@ CFLAGS := $(CFLAGS) @PTHREAD_CFLAGS@
 LDFLAGS := $(LDFLAGS) @PTHREAD_CFLAGS@
 LDLIBS := @PTHREAD_LIBS@ $(LDLIBS)
 endif
-ifeq ($(empthread),LWP)
-# TODO use config.h
-CPPFLAGS += -DUCONTEXT
-endif
 termlibs := @termlibs@
 CCDEPMODE := @CCDEPMODE@
 @am__fastdepCC_TRUE@how_to_dep := fast
diff --git a/configure.ac b/configure.ac
index d3cd103d..8424084c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -118,7 +118,8 @@ esac
 AC_SUBST(empthread)
 AC_MSG_NOTICE([Using $empthread threads])
 case $empthread in
-LWP)	AC_DEFINE([EMPTH_LWP], 1, [Define to use LWP threads]) ;;
+LWP)	AC_DEFINE([EMPTH_LWP], 1, [Define to use LWP threads])
+	AC_DEFINE([UCONTEXT], 1, [Define to make LWP use makecontext()]) ;;
 POSIX)	AC_DEFINE([EMPTH_POSIX], 1, [Define to use POSIX threads]) ;;
 Windows) AC_DEFINE([EMPTH_W32], 1, [Define to use Windows threads]) ;;
 esac