diff --git a/src/Make_ming.mak b/src/Make_ming.mak
index b11db8b..80a0c66 100644
--- a/src/Make_ming.mak
+++ b/src/Make_ming.mak
@@ -384,6 +384,9 @@
 ifeq (yes, $(DYNAMIC_MZSCHEME))
 CFLAGS += -DDYNAMIC_MZSCHEME -DDYNAMIC_MZSCH_DLL=\"lib$(MZSCHEME_MAIN_LIB)$(MZSCHEME_VER).dll\" -DDYNAMIC_MZGC_DLL=\"libmzgc$(MZSCHEME_VER).dll\"
 endif
+ifeq (yes, "$(MZSCHEME_DEBUG)")
+CFLAGS += -DMZSCHEME_FORCE_GC
+endif
 endif
 
 ifdef RUBY