diff --git a/core/envsetup.mk b/core/envsetup.mk
index 6c38e99..46c1463 100644
--- a/core/envsetup.mk
+++ b/core/envsetup.mk
@@ -154,6 +154,10 @@
 ifeq ($(TARGET_ARCH),)
   $(error TARGET_ARCH not defined by board config: $(board_config_mk))
 endif
+ifneq ($(MALLOC_IMPL),)
+  $(warning *** Unsupported option MALLOC_IMPL defined by board config: $(board_config_mk).)
+  $(error Use `MALLOC_SVELTE := true` to configure jemalloc for low-memory)
+endif
 TARGET_DEVICE_DIR := $(patsubst %/,%,$(dir $(board_config_mk)))
 board_config_mk :=