2 files changed, 31 insertions, 20 deletions

diff --git a/src/gc.c b/src/gc.c
index 02e058f88..e31ec2f33 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -613,14 +613,11 @@ gc_mark_children(mrb_state *mrb, mrb_gc *gc, struct RBasic *obj)
   case MRB_TT_ENV:
     {
       struct REnv *e = (struct REnv*)obj;
+      mrb_int i, len;
 
-      if (!MRB_ENV_STACK_SHARED_P(e)) {
-        mrb_int i, len;
-
-        len = MRB_ENV_STACK_LEN(e);
-        for (i=0; i<len; i++) {
-          mrb_gc_mark_value(mrb, e->stack[i]);
-        }
+      len = MRB_ENV_STACK_LEN(e);
+      for (i=0; i<len; i++) {
+        mrb_gc_mark_value(mrb, e->stack[i]);
       }
     }
     break;
@@ -725,9 +722,18 @@ obj_free(mrb_state *mrb, struct RBasic *obj)
   case MRB_TT_FIBER:
     {
       struct mrb_context *c = ((struct RFiber*)obj)->cxt;
-
-      if (c != mrb->root_c)
-        mrb_free_context(mrb, c);
+      if (c && c != mrb->root_c) {
+        mrb_callinfo *ci = c->ci;
+        mrb_callinfo *ce = c->cibase;
+
+        while (ce <= ci) {
+          struct REnv *e = ci->env;
+          if (e && !is_dead(&mrb->gc, e) && MRB_ENV_STACK_SHARED_P(e)) {
+            mrb_env_unshare(mrb, e);
+          }
+          ci--;
+        }
+      }
     }
     break;
 
diff --git a/src/vm.c b/src/vm.c
index b2149b250..58c73e4dd 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -237,22 +237,27 @@ cipush(mrb_state *mrb)
   return ci;
 }
 
+MRB_API void
+mrb_env_unshare(mrb_state *mrb, struct REnv *e)
+{
+  size_t len = (size_t)MRB_ENV_STACK_LEN(e);
+  mrb_value *p = (mrb_value *)mrb_malloc(mrb, sizeof(mrb_value)*len);
+
+  MRB_ENV_UNSHARE_STACK(e);
+  if (len > 0) {
+    stack_copy(p, e->stack, len);
+  }
+  e->stack = p;
+  mrb_write_barrier(mrb, (struct RBasic *)e);
+}
+
 static void
 cipop(mrb_state *mrb)
 {
   struct mrb_context *c = mrb->c;
 
   if (c->ci->env) {
-    struct REnv *e = c->ci->env;
-    size_t len = (size_t)MRB_ENV_STACK_LEN(e);
-    mrb_value *p = (mrb_value *)mrb_malloc(mrb, sizeof(mrb_value)*len);
-
-    MRB_ENV_UNSHARE_STACK(e);
-    if (len > 0) {
-      stack_copy(p, e->stack, len);
-    }
-    e->stack = p;
-    mrb_write_barrier(mrb, (struct RBasic *)e);
+    mrb_env_unshare(mrb, c->ci->env);
   }
 
   c->ci--;