diff --git a/Makefile b/Makefile
index 3fbd8762a..19c7650e2 100644
--- a/Makefile
+++ b/Makefile
@@ -133,8 +133,8 @@ ifeq ($(ENABLE_PYOSYS),1)
 CXXFLAGS += -I$(BREW_PREFIX)/boost/include
 LINKFLAGS += -L$(BREW_PREFIX)/boost/lib -L$(BREW_PREFIX)/boost-python3/lib
 endif
-CXXFLAGS += -I$(BREW_PREFIX)/readline/include
-LINKFLAGS += -L$(BREW_PREFIX)/readline/lib
+CXXFLAGS += -I$(BREW_PREFIX)/readline/include -I$(BREW_PREFIX)/flex/include
+LINKFLAGS += -L$(BREW_PREFIX)/readline/lib -L$(BREW_PREFIX)/flex/lib
 PKG_CONFIG_PATH := $(BREW_PREFIX)/libffi/lib/pkgconfig:$(PKG_CONFIG_PATH)
 PKG_CONFIG_PATH := $(BREW_PREFIX)/tcl-tk/lib/pkgconfig:$(PKG_CONFIG_PATH)
 export PATH := $(BREW_PREFIX)/bison/bin:$(BREW_PREFIX)/gettext/bin:$(BREW_PREFIX)/flex/bin:$(PATH)