diff --git a/.circleci/config.yml b/.circleci/config.yml
index eeb7ad96..90480da9 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -23,11 +23,15 @@ common: &common
 
             bash <(curl -s https://codecov.io/bash) -Z -X gcov -X coveragepy -X search -X xcode -X gcovout -X fix -f coverage.xml -F "${CIRCLE_JOB//-/,}"
 
-            # Coveralls and Codacy do not support merged reports.
-            if [[ "$CIRCLE_JOB" == py36 ]]; then
+            if [[ "$CIRCLE_JOB" != py37-coveragepy5 ]]; then
+              # coveralls-python does not work with Coverage.py 5's data yet.
+              # (https://github.com/coveralls-clients/coveralls-python/issues/203)
               pip install coveralls
-              coveralls
+              COVERALLS_PARALLEL=true coveralls
+            fi
 
+            # Coveralls and Codacy do not support merged reports.
+            if [[ "$CIRCLE_JOB" == py36 ]]; then
               pip install codacy-coverage
               python-codacy-coverage --verbose --report coverage.xml
             fi
@@ -95,3 +99,7 @@ workflows:
       - py34
       - py27
       - checkqa
+
+notify:
+  webhooks:
+    - url: https://coveralls.io/webhook?repo_token=$COVERALLS_REPO_TOKEN
diff --git a/covimerage/cli.py b/covimerage/cli.py
index 8a725e06..1a16adea 100644
--- a/covimerage/cli.py
+++ b/covimerage/cli.py
@@ -51,7 +51,7 @@ def main(ctx, verbose, quiet, loglevel, rcfile):
 
 
 @main.command(name='write_coverage')
-@click.argument('profile_file', type=click.File('r'), required=False, nargs=-1)
+@click.argument('profile_file', type=click.File('r'), required=True, nargs=-1)
 @click.option('--data-file', required=False, type=click.Path(dir_okay=False),
               default=DEFAULT_COVERAGE_DATA_FILE,
               help=('DATA_FILE to write into.  '
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 3fc8dc49..93de3271 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -27,7 +27,7 @@ def test_dunder_main_run_help(capfd):
     assert lines[0].startswith('covimerage, version %s' % get_version())
 
 
-def test_cli(runner, tmpdir):
+def test_cli_write_coverage(runner, tmpdir):
     with tmpdir.as_cwd() as old_dir:
         with pytest.raises(SystemExit) as excinfo:
             cli.write_coverage([os.path.join(
@@ -41,8 +41,15 @@ def test_cli(runner, tmpdir):
             'Error: Invalid value for "profile_file": Could not open file:')
     else:
         assert result.output.splitlines()[-1].startswith(
-            'Error: Invalid value for "[PROFILE_FILE]...": Could not open file:')
+            'Error: Invalid value for "PROFILE_FILE...": Could not open file:')
+    assert result.exit_code == 2
 
+    result = runner.invoke(cli.main, ['write_coverage'])
+    if click.__version__ < '7.0':
+        expected = 'Error: Missing argument "profile_file".'
+    else:
+        expected = 'Error: Missing argument "PROFILE_FILE...".'
+    assert result.output.splitlines()[-1] == expected
     assert result.exit_code == 2
 
 
@@ -306,7 +313,7 @@ def test_cli_call(capfd):
     err_lines = err.splitlines()
     assert err_lines[-1] == (
         'Error: Invalid value for "%s": Could not open file: file not found: No such file or directory' % (
-            "profile_file" if click.__version__ < '7.0' else "[PROFILE_FILE]...",))
+            "profile_file" if click.__version__ < '7.0' else "PROFILE_FILE...",))
     assert out == ''