diff --git a/src/mzscheme/include/scheme.h b/src/mzscheme/include/scheme.h
index cfd348a2df..4186b926bb 100644
--- a/src/mzscheme/include/scheme.h
+++ b/src/mzscheme/include/scheme.h
@@ -1453,6 +1453,7 @@ extern void *scheme_malloc_envunbox(size_t);
 # define MZ_GC_ARRAY_VAR_IN_REG(x, v, l) (__gc_var_stack__[x+2] = (void *)0, \
                                           __gc_var_stack__[x+3] = (void *)&(v), \
                                           __gc_var_stack__[x+4] = (void *)l)
+# define MZ_GC_NO_VAR_IN_REG(x) (__gc_var_stack__[x+2] = NULL)
 # define MZ_GC_REG()  (__gc_var_stack__[0] = GC_variable_stack, \
                        GC_variable_stack = __gc_var_stack__)
 # define MZ_GC_UNREG() (GC_variable_stack = __gc_var_stack__[0])
@@ -1460,6 +1461,7 @@ extern void *scheme_malloc_envunbox(size_t);
 # define MZ_GC_DECL_REG(size)            /* empty */
 # define MZ_GC_VAR_IN_REG(x, v)          /* empty */
 # define MZ_GC_ARRAY_VAR_IN_REG(x, v, l) /* empty */
+# define MZ_GC_NO_VAR_IN_REG(x)          /* empty */
 # define MZ_GC_REG()                     /* empty */
 # define MZ_GC_UNREG()                   /* empty */
 #endif