diff --git a/backend/Makefile b/backend/Makefile
index ed18223..5f9ec78 100644
--- a/backend/Makefile
+++ b/backend/Makefile
@@ -1,7 +1,7 @@
 .POSIX:
 .SUFFIXES:
 HARE=hare
-HAREFLAGS=
+HAREFLAGS ?= -lpthread
 
 DESTDIR=
 PREFIX=/usr/local