4 files changed, 22 insertions, 2 deletions
diff --git a/cont.c b/cont.c
index c56ea0f6e6..8d54b369a6 100644
--- a/cont.c
+++ b/cont.c
@@ -1660,6 +1660,20 @@ rb_fiber_s_current(VALUE klass)
 
 
 
+#ifdef HAVE_WORKING_FORK
+void
+rb_fiber_atfork(rb_thread_t *th)
+{
+    if (th->root_fiber) {
+        if (&th->root_fiber->cont.saved_ec != th->ec) {
+            th->root_fiber = th->ec->fiber_ptr;
+            th->root_fiber->cont.type = ROOT_FIBER_CONTEXT;
+        }
+        th->root_fiber->prev = 0;
+    }
+}
+#endif
+
 /*
  *  Document-class: FiberError
  *
diff --git a/test/ruby/test_fiber.rb b/test/ruby/test_fiber.rb
index ffcb02ce51..dec9f8028b 100644
--- a/test/ruby/test_fiber.rb
+++ b/test/ruby/test_fiber.rb
@@ -256,7 +256,11 @@ class TestFiber < Test::Unit::TestCase
     end
     bug5700 = '[ruby-core:41456]'
     assert_nothing_raised(bug5700) do
-      Fiber.new{ pid = fork {} }.resume
+      Fiber.new do
+        pid = fork do
+          Fiber.new {}.transfer
+        end
+      end.resume
     end
     pid, status = Process.waitpid2(pid)
     assert_equal(0, status.exitstatus, bug5700)
diff --git a/thread.c b/thread.c
index 3992753304..0415ea8c6a 100644
--- a/thread.c
+++ b/thread.c
@@ -4172,12 +4172,14 @@ terminate_atfork_i(rb_thread_t *th, const rb_thread_t *current_th)
     }
 }
 
+void rb_fiber_atfork(rb_thread_t *);
 void
 rb_thread_atfork(void)
 {
     rb_thread_t *th = GET_THREAD();
     rb_thread_atfork_internal(th, terminate_atfork_i);
     th->join_list = NULL;
+    rb_fiber_atfork(th);
 
     /* We don't want reproduce CVE-2003-0900. */
     rb_reset_random_seed();
diff --git a/version.h b/version.h
index 506befeb0a..8f58cf12da 100644
--- a/version.h
+++ b/version.h
@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.4.6"
 #define RUBY_RELEASE_DATE "2019-01-31"
-#define RUBY_PATCHLEVEL 343
+#define RUBY_PATCHLEVEL 344
 
 #define RUBY_RELEASE_YEAR 2019
 #define RUBY_RELEASE_MONTH 1