diff --git a/news/434.bugfix.md b/news/434.bugfix.md
new file mode 100644
index 00000000..7ebde17e
--- /dev/null
+++ b/news/434.bugfix.md
@@ -0,0 +1 @@
+Fixed `parameter_option` returning only the first character of `--option=value` and attached short-option values.
diff --git a/src/cleo/io/inputs/argv_input.py b/src/cleo/io/inputs/argv_input.py
index 54cc1735..710fa544 100644
--- a/src/cleo/io/inputs/argv_input.py
+++ b/src/cleo/io/inputs/argv_input.py
@@ -129,8 +129,8 @@ def parameter_option(
                 # For short options, test for '-o' at beginning
                 leading = value + "=" if value.startswith("--") else value
 
-                if token == value or (leading != "" and token.startswith(leading)):
-                    return token[len(leading)]
+                if leading != "" and token.startswith(leading):
+                    return token[len(leading) :]
 
         return False
 
diff --git a/tests/io/inputs/test_argv_input.py b/tests/io/inputs/test_argv_input.py
index f83ae50f..54561fd3 100644
--- a/tests/io/inputs/test_argv_input.py
+++ b/tests/io/inputs/test_argv_input.py
@@ -151,3 +151,26 @@ def test_parse_options(
     i.bind(Definition(options))
 
     assert i.options == expected_options
+
+
+@pytest.mark.parametrize(
+    ["args", "values", "expected"],
+    [
+        (["cli.py", "--directory", "/tmp/foo"], "--directory", "/tmp/foo"),
+        (["cli.py", "--directory=/tmp/foo"], "--directory", "/tmp/foo"),
+        (["cli.py", "-C", "/tmp/foo"], "-C", "/tmp/foo"),
+        (["cli.py", "-C/tmp/foo"], "-C", "/tmp/foo"),
+        (
+            ["cli.py", "run", "--directory=/tmp/foo", "python"],
+            "--directory",
+            "/tmp/foo",
+        ),
+        (["cli.py", "run", "-C/tmp/foo", "python"], "-C", "/tmp/foo"),
+    ],
+)
+def test_parameter_option_returns_full_attached_value(
+    args: list[str], values: str, expected: str
+) -> None:
+    i = ArgvInput(args)
+
+    assert i.parameter_option(values) == expected