diff --git a/gc.c b/gc.c
index d7971668..ecd54a40 100644
--- a/gc.c
+++ b/gc.c
@@ -523,15 +523,17 @@ void sexp_offset_heap_pointers (sexp_heap heap, sexp_heap from_heap, sexp* types
         sexp_stack_top(sexp_context_stack(p)) = 0;
         sexp_context_saves(p) = NULL;
         sexp_context_heap(p) = heap;
-      } else if (sexp_bytecodep(p)) {
+      } else if (sexp_bytecodep(p) && off != 0) {
         for (i=0; i<sexp_bytecode_length(p); ) {
           switch (sexp_bytecode_data(p)[i++]) {
-            case SEXP_OP_CLOSURE_REF: case SEXP_OP_PUSH:
             case SEXP_OP_FCALL0:      case SEXP_OP_FCALL1:
             case SEXP_OP_FCALL2:      case SEXP_OP_FCALL3:
             case SEXP_OP_FCALL4:      case SEXP_OP_CALL:
-            case SEXP_OP_TAIL_CALL:   case SEXP_OP_PARAMETER_REF:
+            case SEXP_OP_TAIL_CALL:   case SEXP_OP_PUSH:
             case SEXP_OP_GLOBAL_REF:  case SEXP_OP_GLOBAL_KNOWN_REF:
+#if SEXP_USE_GREEN_THREADS
+            case SEXP_OP_PARAMETER_REF:
+#endif
 #if SEXP_USE_EXTENDED_FCALL
             case SEXP_OP_FCALLN:
 #endif
@@ -539,8 +541,9 @@ void sexp_offset_heap_pointers (sexp_heap heap, sexp_heap from_heap, sexp* types
               if (v[0] && sexp_pointerp(v[0])) v[0] = (sexp) (((char*)v[0]) + off);
               /* ... FALLTHROUGH ... */
             case SEXP_OP_JUMP:        case SEXP_OP_JUMP_UNLESS:
-            case SEXP_OP_STACK_REF:   case SEXP_OP_LOCAL_REF:
-            case SEXP_OP_LOCAL_SET:   case SEXP_OP_TYPEP:
+            case SEXP_OP_STACK_REF:   case SEXP_OP_CLOSURE_REF:
+            case SEXP_OP_LOCAL_REF:   case SEXP_OP_LOCAL_SET:
+            case SEXP_OP_TYPEP:
 #if SEXP_USE_RESERVE_OPCODE
             case SEXP_OP_RESERVE:
 #endif
@@ -549,8 +552,6 @@ void sexp_offset_heap_pointers (sexp_heap heap, sexp_heap from_heap, sexp* types
               i += 2*sizeof(sexp); break;
             case SEXP_OP_MAKE_PROCEDURE:
               v = (sexp*)(&(sexp_bytecode_data(p)[i]));
-              if (v[0] && sexp_pointerp(v[0])) v[0] = (sexp) (((char*)v[0]) + off);
-              if (v[1] && sexp_pointerp(v[1])) v[1] = (sexp) (((char*)v[1]) + off);
               if (v[2] && sexp_pointerp(v[2])) v[2] = (sexp) (((char*)v[2]) + off);
               i += 3*sizeof(sexp); break;
           }
diff --git a/vm.c b/vm.c
index aac5eec1..12dd0b69 100644
--- a/vm.c
+++ b/vm.c
@@ -1135,7 +1135,7 @@ sexp sexp_apply (sexp ctx, sexp proc, sexp args) {
     break;
   case SEXP_OP_CLOSURE_REF:
     _ALIGN_IP();
-    _PUSH(sexp_vector_ref(cp, sexp_make_fixnum(_WORD0)));
+    _PUSH(sexp_vector_ref(cp, sexp_make_fixnum(_SWORD0)));
     ip += sizeof(sexp);
     break;
   case SEXP_OP_CLOSURE_VARS: