diff --git a/mk/main.mk b/mk/main.mk
index e892286f7fd..99aecc34be9 100644
--- a/mk/main.mk
+++ b/mk/main.mk
@@ -123,11 +123,9 @@ CFG_JEMALLOC_FLAGS += $(JEMALLOC_FLAGS)
 
 ifdef CFG_DISABLE_DEBUG
   CFG_RUSTC_FLAGS += --cfg ndebug
-  CFG_GCCISH_CFLAGS += -DRUST_NDEBUG
 else
   $(info cfg: enabling more debugging (CFG_ENABLE_DEBUG))
   CFG_RUSTC_FLAGS += --cfg debug
-  CFG_GCCISH_CFLAGS += -DRUST_DEBUG
 endif
 
 ifdef SAVE_TEMPS