diff --git a/src/Makefile b/src/Makefile
index 75dffb24e..3e1a146e5 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -258,6 +258,7 @@ endif
 ifeq ($(BUILD_WITH_SYSTEMD),yes)
 	FINAL_LIBS+=$(LIBSYSTEMD_LIBS)
 	FINAL_CFLAGS+= -DHAVE_LIBSYSTEMD
+	FINAL_CXXFLAGS+= -DHAVE_LIBSYSTEMD
 endif
 
 ifeq ($(MALLOC),tcmalloc)