diff --git a/Makefile b/Makefile
index 88806a3d5b5ed1772f04779eddcb8db6913b4788..3de49d45d85894aa1d9edafde97d5e3e3f575d7a 100644
--- a/Makefile
+++ b/Makefile
@@ -7,6 +7,9 @@ ifeq "${OS}" "Linux"
 CFLAGS += -flto
 CXXFLAGS += -flto
 LFLAGS += -flto
+else ifeq "${OS}" "FreeBSD"
+CFLAGS += -Wno-error=sign-conversion
+CXXFLAGS += -Wno-error=sign-conversion
 endif
 
 CC ?= gcc