diff --git a/include/cyclone/runtime.h b/include/cyclone/runtime.h
index 240abbaf..51392fc2 100644
--- a/include/cyclone/runtime.h
+++ b/include/cyclone/runtime.h
@@ -73,6 +73,7 @@ object Cyc_global_set(void *thd, object *glo, object value);
             tmp = arg_var; \
         } \
         var[i].hdr.mark = gc_color_red; \
+        var[i].hdr.grayed = 0; \
         var[i].tag = cons_tag; \
         var[i].cons_car = tmp; \
         var[i].cons_cdr = (i == (count-1)) ? nil : &var[i + 1]; \
diff --git a/include/cyclone/types.h b/include/cyclone/types.h
index 3b6c85b6..9ca3af8b 100644
--- a/include/cyclone/types.h
+++ b/include/cyclone/types.h
@@ -260,7 +260,7 @@ typedef void (*function_type_va)(int, object, object, object, ...);
 /* Define C-variable integration type */
 typedef struct {gc_header_type hdr; tag_type tag; object *pvar;} cvar_type;
 typedef cvar_type *cvar;
-#define make_cvar(n,v) cvar_type n; n.hdr.mark = gc_color_red; n.tag = cvar_tag; n.pvar = v;
+#define make_cvar(n,v) cvar_type n; n.hdr.mark = gc_color_red; n.hdr.grayed = 0; n.tag = cvar_tag; n.pvar = v;
 
 /* Define boolean type. */
 typedef struct {gc_header_type hdr; const tag_type tag; const char *pname;} boolean_type;
@@ -281,9 +281,9 @@ static object quote_##name = nil;
 
 /* Define numeric types */
 typedef struct {gc_header_type hdr; tag_type tag; int value;} integer_type;
-#define make_int(n,v) integer_type n; n.hdr.mark = gc_color_red; n.tag = integer_tag; n.value = v;
+#define make_int(n,v) integer_type n; n.hdr.mark = gc_color_red; n.hdr.grayed = 0; n.tag = integer_tag; n.value = v;
 typedef struct {gc_header_type hdr; tag_type tag; double value;} double_type;
-#define make_double(n,v) double_type n; n.hdr.mark = gc_color_red; n.tag = double_tag; n.value = v;
+#define make_double(n,v) double_type n; n.hdr.mark = gc_color_red; n.hdr.grayed = 0; n.tag = double_tag; n.value = v;
 
 #define integer_value(x) (((integer_type *) x)->value)
 #define double_value(x) (((double_type *) x)->value)
@@ -294,16 +294,16 @@ typedef struct {gc_header_type hdr; tag_type tag; int len; char *str;} string_ty
 //// all functions that allocate strings, the GC, cgen, and maybe more.
 //// Because these strings are (at least for now) allocaed on the stack.
 #define make_string(cs, s) string_type cs; \
-{ int len = strlen(s); cs.tag = string_tag; cs.len = len; cs.hdr.mark = gc_color_red; \
+{ int len = strlen(s); cs.tag = string_tag; cs.len = len; cs.hdr.mark = gc_color_red; n.hdr.grayed = 0; \
   cs.str = alloca(sizeof(char) * (len + 1)); \
   memcpy(cs.str, s, len + 1);}
-#define make_string_with_len(cs, s, length) string_type cs; cs.hdr.mark = gc_color_red; \
+#define make_string_with_len(cs, s, length) string_type cs; cs.hdr.mark = gc_color_red; n.hdr.grayed = 0; \
 { int len = length; \
   cs.tag = string_tag; cs.len = len; \
   cs.str = alloca(sizeof(char) * (len + 1)); \
   memcpy(cs.str, s, len); \
   cs.str[len] = '\0';}
-#define make_string_noalloc(cs, s, length) string_type cs; cs.hdr.mark = gc_color_red; \
+#define make_string_noalloc(cs, s, length) string_type cs; cs.hdr.mark = gc_color_red; n.hdr.grayed = 0; \
 { cs.tag = string_tag; cs.len = length; \
   cs.str = s; }
 
@@ -317,14 +317,14 @@ typedef struct {gc_header_type hdr; tag_type tag; int len; char *str;} string_ty
 // TODO: a simple wrapper around FILE may not be good enough long-term
 // TODO: how exactly mode will be used. need to know r/w, bin/txt
 typedef struct {gc_header_type hdr; tag_type tag; FILE *fp; int mode;} port_type;
-#define make_port(p,f,m) port_type p; p.hdr.mark = gc_color_red; p.tag = port_tag; p.fp = f; p.mode = m;
+#define make_port(p,f,m) port_type p; p.hdr.mark = gc_color_red; n.hdr.grayed = 0; p.tag = port_tag; p.fp = f; p.mode = m;
 
 /* Vector type */
 
 typedef struct {gc_header_type hdr; tag_type tag; int num_elt; object *elts;} vector_type;
 typedef vector_type *vector;
 
-#define make_empty_vector(v) vector_type v; v.hdr.mark = gc_color_red; v.tag = vector_tag; v.num_elt = 0; v.elts = NULL;
+#define make_empty_vector(v) vector_type v; v.hdr.mark = gc_color_red; n.hdr.grayed = 0; v.tag = vector_tag; v.num_elt = 0; v.elts = NULL;
 
 /* Define cons type. */
 
@@ -363,7 +363,7 @@ typedef cons_type *list;
 #define cddddr(x) (cdr(cdr(cdr(cdr(x)))))
 
 #define make_cons(n,a,d) \
-cons_type n; n.hdr.mark = gc_color_red; n.tag = cons_tag; n.cons_car = a; n.cons_cdr = d;
+cons_type n; n.hdr.mark = gc_color_red; n.hdr.grayed = 0; n.tag = cons_tag; n.cons_car = a; n.cons_cdr = d;
 
 /* Closure types */
 
@@ -384,15 +384,15 @@ typedef closureN_type *closureN;
 typedef closure0_type *closure;
 typedef closure0_type *macro;
 
-#define mmacro(c,f) macro_type c; c.hdr.mark = gc_color_red; c.tag = macro_tag; c.fn = f; c.num_args = -1;
-#define mclosure0(c,f) closure0_type c; c.hdr.mark = gc_color_red; c.tag = closure0_tag; c.fn = f; c.num_args = -1;
-#define mclosure1(c,f,a) closure1_type c; c.hdr.mark = gc_color_red; c.tag = closure1_tag; \
+#define mmacro(c,f) macro_type c; c.hdr.mark = gc_color_red; n.hdr.grayed = 0; c.tag = macro_tag; c.fn = f; c.num_args = -1;
+#define mclosure0(c,f) closure0_type c; c.hdr.mark = gc_color_red; n.hdr.grayed = 0; c.tag = closure0_tag; c.fn = f; c.num_args = -1;
+#define mclosure1(c,f,a) closure1_type c; c.hdr.mark = gc_color_red; n.hdr.grayed = 0; c.tag = closure1_tag; \
    c.fn = f; c.num_args = -1; c.elt1 = a;
-#define mclosure2(c,f,a1,a2) closure2_type c; c.hdr.mark = gc_color_red; c.tag = closure2_tag; \
+#define mclosure2(c,f,a1,a2) closure2_type c; c.hdr.mark = gc_color_red; n.hdr.grayed = 0; c.tag = closure2_tag; \
    c.fn = f; c.num_args = -1; c.elt1 = a1; c.elt2 = a2;
-#define mclosure3(c,f,a1,a2,a3) closure3_type c; c.hdr.mark = gc_color_red; c.tag = closure3_tag; \
+#define mclosure3(c,f,a1,a2,a3) closure3_type c; c.hdr.mark = gc_color_red; n.hdr.grayed = 0; c.tag = closure3_tag; \
    c.fn = f; c.num_args = -1; c.elt1 = a1; c.elt2 = a2; c.elt3 = a3;
-#define mclosure4(c,f,a1,a2,a3,a4) closure4_type c; c.hdr.mark = gc_color_red; c.tag = closure4_tag; \
+#define mclosure4(c,f,a1,a2,a3,a4) closure4_type c; c.hdr.mark = gc_color_red; n.hdr.grayed = 0; c.tag = closure4_tag; \
    c.fn = f; c.num_args = -1; c.elt1 = a1; c.elt2 = a2; c.elt3 = a3; c.elt4 = a4;
 
 #define mlist1(e1) (mcons(e1,nil))
diff --git a/runtime.c b/runtime.c
index 11ad7906..d1a60d20 100644
--- a/runtime.c
+++ b/runtime.c
@@ -942,11 +942,13 @@ common_type Cyc_string2number(void *data, object str){
 
         if (ceilf(n) == n) {
             result.integer_t.hdr.mark = gc_color_red;
+            result.integer_t.hdr.grayed = 0;
             result.integer_t.tag = integer_tag;
             result.integer_t.value = (int)n;
         }
         else {
             result.double_t.hdr.mark = gc_color_red;
+            result.double_t.hdr.grayed = 0;
             result.double_t.tag = double_tag;
             result.double_t.value = n;
         }
@@ -1129,6 +1131,7 @@ object Cyc_command_line_arguments(void *data, object cont) {
     make_string(s, _cyc_argv[i - 1]);
     memcpy(ps, &s, sizeof(string_type));
     ((list)pl)->hdr.mark = gc_color_red;
+    ((list)pl)->hdr.grayed = 0;
     ((list)pl)->tag = cons_tag;
     ((list)pl)->cons_car = ps;
     ((list)pl)->cons_cdr = lis;
@@ -1143,6 +1146,7 @@ object Cyc_make_vector(void *data, object cont, object len, object fill) {
   Cyc_check_int(data, len);
   v = alloca(sizeof(vector_type));
   ((vector)v)->hdr.mark = gc_color_red;
+  ((vector)v)->hdr.grayed = 0;
   ((vector)v)->tag = vector_tag;
   ((vector)v)->num_elt = ((integer_type *)len)->value;
   ((vector)v)->elts = 
@@ -1165,6 +1169,7 @@ object Cyc_list2vector(void *data, object cont, object l) {
   len = Cyc_length(data, l); 
   v = alloca(sizeof(vector_type)); 
   ((vector)v)->hdr.mark = gc_color_red;
+  ((vector)v)->hdr.grayed = 0;
   ((vector)v)->tag = vector_tag; 
   ((vector)v)->num_elt = len.value; 
   ((vector)v)->elts = 
@@ -1223,6 +1228,7 @@ common_type FUNC_OP(void *data, object x, object y) { \
     common_type s; \
     int tx = type_of(x), ty = type_of(y); \
     s.double_t.hdr.mark = gc_color_red; \
+    s.double_t.hdr.grayed = 0; \
     s.double_t.tag = double_tag; \
     if (DIV &&  \
         ((ty == integer_tag && integer_value(y) == 0) || \
@@ -1231,6 +1237,7 @@ common_type FUNC_OP(void *data, object x, object y) { \
     } \
     if (tx == integer_tag && ty == integer_tag) { \
         s.integer_t.hdr.mark = gc_color_red; \
+        s.integer_t.hdr.grayed = 0; \
         s.integer_t.tag = integer_tag; \
         s.integer_t.value = ((integer_type *)x)->value OP ((integer_type *)y)->value; \
     } else if (tx == double_tag && ty == integer_tag) { \
@@ -1274,6 +1281,7 @@ common_type Cyc_num_op_va_list(void *data, int argc, common_type (fn_op(void *,
   int i;
   if (argc == 0) {
     sum.integer_t.hdr.mark = gc_color_red;
+    sum.integer_t.hdr.grayed = 0;
     sum.integer_t.tag = integer_tag;
     sum.integer_t.value = 0;
     return sum;
@@ -1281,10 +1289,12 @@ common_type Cyc_num_op_va_list(void *data, int argc, common_type (fn_op(void *,
 
   if (type_of(n) == integer_tag) {
     sum.integer_t.hdr.mark = gc_color_red;
+    sum.integer_t.hdr.grayed = 0; 
     sum.integer_t.tag = integer_tag;
     sum.integer_t.value = ((integer_type *)n)->value;
   } else if (type_of(n) == double_tag) {
     sum.double_t.hdr.mark = gc_color_red;
+    sum.double_t.hdr.grayed = 0;
     sum.double_t.tag = double_tag;
     sum.double_t.value = ((double_type *)n)->value;
   } else {
@@ -1298,10 +1308,12 @@ common_type Cyc_num_op_va_list(void *data, int argc, common_type (fn_op(void *,
     common_type result = fn_op(data, &sum, va_arg(ns, object));
     if (type_of(&result) == integer_tag) {
         sum.integer_t.hdr.mark = gc_color_red;
+        sum.integer_t.hdr.grayed = 0;
         sum.integer_t.tag = integer_tag;
         sum.integer_t.value = ((integer_type *) &result)->value;
     } else if (type_of(&result) == double_tag) {
         sum.double_t.hdr.mark = gc_color_red;
+        sum.double_t.hdr.grayed = 0;
         sum.double_t.tag = double_tag;
         sum.double_t.value = ((double_type *) &result)->value;
     } else {
@@ -1454,12 +1466,14 @@ object Cyc_io_peek_char(void *data, object port) {
 list mcons(a,d) object a,d;
 {register cons_type *c = malloc(sizeof(cons_type));
  c->hdr.mark = gc_color_red;
+ c->hdr.grayed = 0;
  c->tag = cons_tag; c->cons_car = a; c->cons_cdr = d;
  return c;}
 
 cvar_type *mcvar(object *var) {
   cvar_type *c = malloc(sizeof(cvar_type));
   c->hdr.mark = gc_color_red;
+  c->hdr.grayed = 0;
   c->tag = cvar_tag; 
   c->pvar = var;
   return c;}
@@ -1955,6 +1969,7 @@ void Cyc_apply(void *data, int argc, closure cont, object prim, ...){
     for (i = 0; i < argc; i++) {
         tmp = va_arg(ap, object);
         args[i].hdr.mark = gc_color_red;
+        args[i].hdr.grayed = 0;
         args[i].tag = cons_tag;
         args[i].cons_car = tmp;
         args[i].cons_cdr = (i == (argc-1)) ? nil : &args[i + 1];
@@ -1984,6 +1999,7 @@ void Cyc_apply_from_buf(void *data, int argc, object prim, object *buf) {
     
     for (i = 1; i < argc; i++) {
         args[i - 1].hdr.mark = gc_color_red;
+        args[i - 1].hdr.grayed = 0;
         args[i - 1].tag = cons_tag;
         args[i - 1].cons_car = buf[i];
         args[i - 1].cons_cdr = (i == (argc-1)) ? nil : &args[i];
diff --git a/scheme/cyclone/cgen.sld b/scheme/cyclone/cgen.sld
index 2c218a1d..50ca02ae 100644
--- a/scheme/cyclone/cgen.sld
+++ b/scheme/cyclone/cgen.sld
@@ -1087,6 +1087,7 @@
            (string-append
              "closureN_type " cv-name ";\n"
              cv-name ".hdr.mark = gc_color_red;\n "
+             cv-name ".hdr.grayed = 0;\n"
              cv-name ".tag = closureN_tag;\n "
              cv-name ".fn = (function_type)__lambda_" (number->string lid) ";\n"
              cv-name ".num_args = " (number->string (compute-num-args lam)) ";\n"