diff --git a/ports/stm32/Makefile b/ports/stm32/Makefile
index 61ce06ca8c..c9fdc7b0d2 100644
--- a/ports/stm32/Makefile
+++ b/ports/stm32/Makefile
@@ -408,6 +408,10 @@ ifneq ($(MICROPY_PY_WIZNET5K),0)
 WIZNET5K_DIR=drivers/wiznet5k
 INC += -I$(TOP)/$(WIZNET5K_DIR)
 CFLAGS_MOD += -DMICROPY_PY_WIZNET5K=$(MICROPY_PY_WIZNET5K) -D_WIZCHIP_=$(MICROPY_PY_WIZNET5K)
+ifeq ($(MICROPY_PY_LWIP),1)
+# When using MACRAW mode (with lwIP), maximum buffer space must be used for the raw socket
+CFLAGS_MOD += -DWIZCHIP_USE_MAX_BUFFER
+endif
 SRC_MOD += network_wiznet5k.c modnwwiznet5k.c
 SRC_MOD += $(addprefix $(WIZNET5K_DIR)/,\
 	ethernet/w$(MICROPY_PY_WIZNET5K)/w$(MICROPY_PY_WIZNET5K).c \