diff --git a/src/test/Makefile b/src/test/Makefile
index 0696ff299..3cf646640 100644
--- a/src/test/Makefile
+++ b/src/test/Makefile
@@ -38,6 +38,7 @@ C_FLAGS = $(COMMON_FLAGS) \
 
 # Flags passed to the C++ compiler.
 CXX_FLAGS = $(COMMON_FLAGS) \
+	-lpthread
 	-std=c++11
 
 # All tests produced by this Makefile.  Remember to add new tests you