diff --git a/mdformat_mkdocs/plugin.py b/mdformat_mkdocs/plugin.py
index e01c9d2..c387476 100644
--- a/mdformat_mkdocs/plugin.py
+++ b/mdformat_mkdocs/plugin.py
@@ -59,12 +59,21 @@ class _MarkdownList:
     is_semantic_indent = False
     is_list_match = False
 
+    _numbered = None
+
     def __init__(self, increment_number_mode: bool) -> None:
         """Store relevant 'mdformat' context."""
         self.increment_number_mode = increment_number_mode
 
     def _number(self) -> int:
         """Return the number."""
+        if self.increment_number_mode:
+            idx = len(self.this_indent)
+            pad = [0] * (idx + 1)
+            # FYI: on de-dent, clip previously saved _numbered
+            self._numbered = [*(self._numbered or []), *pad][: (idx + 1)]
+            self._numbered[idx] += 1
+            return self._numbered[idx]
         return 1
 
     def add_bullet(self, line: str) -> str:
diff --git a/tests/test_number.py b/tests/test_number.py
new file mode 100644
index 0000000..b30c777
--- /dev/null
+++ b/tests/test_number.py
@@ -0,0 +1,71 @@
+import mdformat
+import pytest
+
+CASE_1 = """
+1. One
+    1. AAA
+    1. BBB
+    1. CCC
+1. Two
+1. Three
+1. Four
+    1. AAA
+    1. BBB
+    1. CCC
+1. Five
+1. Six
+    1. AAA
+    1. BBB
+    1. CCC
+        1. aaa
+        1. bbb
+        1. ccc
+        1. ddd
+1. Seven
+"""
+
+
+CASE_1_NUMBERED = """
+1. One
+    1. AAA
+    2. BBB
+    3. CCC
+2. Two
+3. Three
+4. Four
+    1. AAA
+    2. BBB
+    3. CCC
+5. Five
+6. Six
+    1. AAA
+    2. BBB
+    3. CCC
+        1. aaa
+        2. bbb
+        3. ccc
+        4. ddd
+7. Seven
+"""
+
+
+@pytest.mark.parametrize(
+    "text,expected",
+    [
+        (CASE_1, CASE_1_NUMBERED),
+    ],
+    ids=[
+        "CASE_1_NUMBERED",
+    ],
+)
+def test_number(text: str, expected: str):
+    output = mdformat.text(
+        text,
+        options={"number": True},
+        extensions={"mkdocs"},
+    )
+
+    print(output.strip())
+    print("-- Expected --")
+    print(expected.strip())
+    assert output.strip() == expected.strip()