diff --git a/Lib/json/tool.py b/Lib/json/tool.py
index 0490b8c0be11dfe..a0a8233ec61b501 100644
--- a/Lib/json/tool.py
+++ b/Lib/json/tool.py
@@ -69,6 +69,10 @@ def main():
             if options.outfile is None:
                 out = sys.stdout
             else:
+                if (options.outfile.exists() and
+                    options.outfile.expanduser().samefile(infile.name)):
+                    # exhaust the generator before opening for writing
+                    objs = list(objs)
                 out = options.outfile.open('w', encoding='utf-8')
             with out as outfile:
                 for obj in objs:
diff --git a/Lib/test/support/script_helper.py b/Lib/test/support/script_helper.py
index 6d699c8486cd20d..10b04950a82ec48 100644
--- a/Lib/test/support/script_helper.py
+++ b/Lib/test/support/script_helper.py
@@ -2,6 +2,7 @@
 #  e.g. test_cmd_line, test_cmd_line_script and test_runpy
 
 import collections
+import contextlib
 import importlib
 import sys
 import os
@@ -196,9 +197,12 @@ def spawn_python(*args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, **kw):
 
 def kill_python(p):
     """Run the given Popen process until completion and return stdout."""
-    p.stdin.close()
-    data = p.stdout.read()
-    p.stdout.close()
+    data = None
+    if p.stdin:
+        p.stdin.close()
+    if p.stdout:
+        data = p.stdout.read()
+        p.stdout.close()
     # try to cleanup the child so we don't appear to leak when running
     # with regrtest -R.
     p.wait()
@@ -206,6 +210,16 @@ def kill_python(p):
     return data
 
 
+@contextlib.contextmanager
+def killing(process):
+    """Context manager that kills and cleans up the given Popen on exit."""
+    try:
+        yield process
+    finally:
+        process.kill()
+        kill_python(process)
+
+
 def make_script(script_dir, script_basename, source, omit_suffix=False):
     script_filename = script_basename
     if not omit_suffix:
diff --git a/Lib/test/test_json/test_tool.py b/Lib/test/test_json/test_tool.py
index 1d7fca6efb1cc72..c67f9115a93479a 100644
--- a/Lib/test/test_json/test_tool.py
+++ b/Lib/test/test_json/test_tool.py
@@ -7,7 +7,7 @@
 
 from test import support
 from test.support import os_helper
-from test.support.script_helper import assert_python_ok
+from test.support.script_helper import assert_python_ok, killing
 
 
 class TestTool(unittest.TestCase):
@@ -146,6 +146,40 @@ def test_jsonlines(self):
         self.assertEqual(process.stdout, self.jsonlines_expect)
         self.assertEqual(process.stderr, '')
 
+    def test_writing_jsonlines_in_place(self):
+        infile = self._create_infile(data=self.jsonlines_raw)
+        rc, out, err = assert_python_ok('-m', 'json.tool', '--json-lines', infile, infile)
+        with open(infile, "r", encoding="utf-8") as fp:
+            self.assertEqual(fp.read(), self.jsonlines_expect)
+        self.assertEqual(rc, 0)
+        self.assertEqual(out, b'')
+        self.assertEqual(err, b'')
+
+    def test_jsonlines_from_a_stream(self):
+        stream_code = textwrap.dedent("""
+        # print a stream of JSON integers
+        i = 0
+        while True:
+            print(i)
+            i += 1
+        """)
+        stream = subprocess.Popen((sys.executable, '-u', '-c', stream_code),
+                                  stdout=subprocess.PIPE,
+                                  bufsize=0,
+                                  )
+        args = sys.executable, '-u', '-m', 'json.tool', '--json-lines'
+        with killing(stream), \
+                self.assertRaises(subprocess.TimeoutExpired) as timeout:
+            subprocess.run(args, stdin=stream.stdout,
+                           capture_output=True, timeout=1,
+                           bufsize=0)
+
+        self.assertIsNotNone(timeout.exception.stdout)
+        self.assertEqual(
+            timeout.exception.stdout.splitlines()[:3],
+            [b'0', b'1', b'2']
+        )
+
     def test_help_flag(self):
         rc, out, err = assert_python_ok('-m', 'json.tool', '-h')
         self.assertEqual(rc, 0)