diff --git a/Changelog.rst b/Changelog.rst
index 02cd37e..df09155 100644
--- a/Changelog.rst
+++ b/Changelog.rst
@@ -4,6 +4,16 @@
  Change history
 ================
 
+.. _version-unreleased:
+
+Unreleased
+==========
+
+- Do not offer true/false value completions for boolean flags (``is_flag=True``,
+  including ``--foo/--no-foo`` style options), which previously inserted a value
+  into the positional-argument slot (#116).
+
+
 .. _version-0.3.0:
 
 0.3.0
diff --git a/click_repl/_completer.py b/click_repl/_completer.py
index 73a769c..5556607 100644
--- a/click_repl/_completer.py
+++ b/click_repl/_completer.py
@@ -173,7 +173,13 @@ def _get_completion_from_params(
         choices: list[Completion] = []
         param_type = param.type
 
-        # shell_complete method for click.Choice is intorduced in click-v8
+        # Flags (is_flag=True, incl. secondary opts like --foo/--no-foo) do not
+        # consume a value, so we must not offer any value completions for them.
+        # See https://github.com/click-contrib/click-repl/issues/116
+        if getattr(param, "is_flag", False):
+            return choices
+
+        # shell_complete method for click.Choice was introduced in Click v8
         if not HAS_CLICK_V8 and isinstance(param_type, click.Choice):
             choices.extend(
                 self._get_completion_from_choices_click_le_7(param, incomplete)
diff --git a/tests/test_completion/test_common_tests/test_option_completion.py b/tests/test_completion/test_common_tests/test_option_completion.py
index b4b2659..ff8b89b 100644
--- a/tests/test_completion/test_common_tests/test_option_completion.py
+++ b/tests/test_completion/test_common_tests/test_option_completion.py
@@ -38,6 +38,38 @@ def bool_option(foo):
     assert {x.text for x in completions} == {"true"}
 
 
+def test_flag_option_offers_no_value():
+    # A flag (is_flag=True) does not consume a value, so once it has been
+    # typed the completer must not offer true/false as if it needed one.
+    # See https://github.com/click-contrib/click-repl/issues/116
+    @root_command.command()
+    @click.argument("arg1", type=click.STRING)
+    @click.option("-b", "--some-option", "some_option", is_flag=True)
+    def flag_option(arg1, some_option):
+        pass
+
+    completions = list(c.get_completions(Document("flag-option -b ")))
+    assert {x.text for x in completions} == set()
+
+    completions = list(c.get_completions(Document("flag-option --some-option ")))
+    assert {x.text for x in completions} == set()
+
+
+def test_boolean_flag_with_secondary_opts_offers_no_value():
+    # Flags declared with a secondary option (--foo/--no-foo) are also flags
+    # and must not trigger true/false value completions.
+    @root_command.command()
+    @click.option("--shout/--no-shout", default=False)
+    def toggle_flag(shout):
+        pass
+
+    completions = list(c.get_completions(Document("toggle-flag --shout ")))
+    assert {x.text for x in completions} == set()
+
+    completions = list(c.get_completions(Document("toggle-flag --no-shout ")))
+    assert {x.text for x in completions} == set()
+
+
 def test_only_unused_with_unique_option():
     @root_command.command()
     @click.option("-u", type=click.BOOL)