diff --git a/gc.c b/gc.c
index 6f58fdd6..170c6438 100644
--- a/gc.c
+++ b/gc.c
@@ -347,6 +347,13 @@ char *gc_copy_obj(object dest, char *obj, gc_thread_data *thd)
       hp->pvar = ((cvar_type *) obj)->pvar;
       return (char *)hp;
     }
+    case c_opaque_tag: {
+      c_opaque_type *hp = dest;
+      mark(hp) = thd->gc_alloc_color;
+      type_of(hp) = c_opaque_tag;
+      hp->ptr = ((c_opaque_type *) obj)->ptr;
+      return (char *)hp;
+    }
     case mutex_tag: {
       mutex_type *hp = dest;
       mark(hp) = thd->gc_alloc_color;
@@ -527,6 +534,7 @@ size_t gc_allocated_bytes(object obj, gc_free_list *q, gc_free_list *r)
   if (t == double_tag) return gc_heap_align(sizeof(double_type));
   if (t == port_tag) return gc_heap_align(sizeof(port_type));
   if (t == cvar_tag) return gc_heap_align(sizeof(cvar_type));
+  if (t == c_opaque_tag) return gc_heap_align(sizeof(c_opaque_type));
   if (t == mutex_tag) return gc_heap_align(sizeof(mutex_type));
   if (t == cond_var_tag) return gc_heap_align(sizeof(cond_var_type));
   
diff --git a/runtime.c b/runtime.c
index ed238a24..2375e799 100644
--- a/runtime.c
+++ b/runtime.c
@@ -2831,9 +2831,12 @@ char *gc_move(char *obj, gc_thread_data *thd, int *alloci, int *heap_grown) {
       cvar_type *hp = gc_alloc(Cyc_heap, sizeof(cvar_type), obj, thd, heap_grown);
       return gc_fixup_moved_obj(thd, alloci, obj, hp);
     }
+    case c_opaque_tag: {
+      c_opaque_type *hp = gc_alloc(Cyc_heap, sizeof(c_opaque_type), obj, thd, heap_grown);
+      return gc_fixup_moved_obj(thd, alloci, obj, hp);
+    }
     case forward_tag:
       return (char *)forward(obj);
-    case c_opaque_tag: break;
     case eof_tag: break;
     case primitive_tag: break;
     case boolean_tag: break;
@@ -2965,9 +2968,9 @@ int gc_minor(void *data, object low_limit, object high_limit, closure cont, obje
       case double_tag:
       case port_tag:
       case cvar_tag:
+      case c_opaque_tag:
         break;
       // These types are not heap-allocated
-      case c_opaque_tag:
       case eof_tag:
       case primitive_tag:
       case symbol_tag: