diff --git a/gc.c b/gc.c
index 0cf491b5..45346ddc 100644
--- a/gc.c
+++ b/gc.c
@@ -187,6 +187,9 @@ int sexp_valid_object_p (sexp ctx, sexp x) {
 #endif
 
 void sexp_mark (sexp ctx, sexp x) {
+#if SEXP_USE_CONSERVATIVE_CODE_GC
+  unsigned char *ip;
+#endif
   sexp_sint_t len;
   sexp t, *p, *q;
   struct sexp_gc_var_t *saves;
@@ -194,9 +197,39 @@ void sexp_mark (sexp ctx, sexp x) {
   if (!x || !sexp_pointerp(x) || !sexp_valid_object_p(ctx, x) || sexp_markedp(x))
     return;
   sexp_markedp(x) = 1;
-  if (sexp_contextp(x))
+  if (sexp_contextp(x)) {
     for (saves=sexp_context_saves(x); saves; saves=saves->next)
       if (saves->var) sexp_mark(ctx, *(saves->var));
+  }
+#if SEXP_USE_CONSERVATIVE_CODE_GC
+  else if (sexp_bytecodep(x)) {
+    ip = sexp_bytecode_data(x);
+    while (ip - sexp_bytecode_data(x) < sexp_bytecode_length(x)) {
+      switch (*ip++) {
+      case SEXP_OP_GLOBAL_REF:     case SEXP_OP_GLOBAL_KNOWN_REF:
+      case SEXP_OP_PARAMETER_REF:  case SEXP_OP_TAIL_CALL:
+      case SEXP_OP_CALL:           case SEXP_OP_PUSH:
+        sexp_mark(ctx, ((sexp*)ip)[0]);
+        /* ... FALLTHROUGH ... */
+      case SEXP_OP_JUMP:           case SEXP_OP_JUMP_UNLESS:
+      case SEXP_OP_CLOSURE_REF:    case SEXP_OP_STACK_REF:
+      case SEXP_OP_LOCAL_REF:      case SEXP_OP_LOCAL_SET:
+      case SEXP_OP_RESERVE:        case SEXP_OP_TYPEP:
+        ip += sizeof(sexp);
+        break;
+      case SEXP_OP_SLOT_REF: case SEXP_OP_SLOT_SET: case SEXP_OP_MAKE:
+        ip += sizeof(sexp)*2;
+        break;
+      case SEXP_OP_MAKE_PROCEDURE:
+        sexp_mark(ctx, ((sexp*)ip)[2]);
+        ip += sizeof(sexp)*3;
+        break;
+      default:
+        break;
+      }
+    }
+  }
+#endif
   t = sexp_object_type(ctx, x);
   len = sexp_type_num_slots_of_object(t, x) - 1;
   if (len >= 0) {
diff --git a/include/chibi/features.h b/include/chibi/features.h
index 968111b2..ad1059c2 100644
--- a/include/chibi/features.h
+++ b/include/chibi/features.h
@@ -372,6 +372,10 @@
 #define SEXP_USE_CONSERVATIVE_GC 0
 #endif
 
+#ifndef SEXP_USE_CONSERVATIVE_CODE_GC
+#define SEXP_USE_CONSERVATIVE_CODE_GC 0
+#endif
+
 #ifndef SEXP_USE_TRACK_ALLOC_SOURCE
 #define SEXP_USE_TRACK_ALLOC_SOURCE SEXP_USE_DEBUG_GC > 2
 #endif