diff --git a/mdit_py_plugins/tasklists/__init__.py b/mdit_py_plugins/tasklists/__init__.py
index c508812..40a6d67 100644
--- a/mdit_py_plugins/tasklists/__init__.py
+++ b/mdit_py_plugins/tasklists/__init__.py
@@ -16,12 +16,18 @@
 # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 # OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
+import re
 from typing import List
 from uuid import uuid4
 
 from markdown_it import MarkdownIt
 from markdown_it.token import Token
 
+# Regex string to match a whitespace character, as specified in
+# https://github.github.com/gfm/#whitespace-character
+# (spec version 0.29-gfm (2019-04-06))
+_GFM_WHITESPACE_RE = r"[ \t\n\v\f\r]"
+
 
 def tasklists_plugin(
     md: MarkdownIt,
@@ -144,8 +150,4 @@ def is_list_item(token):
 
     def starts_with_todo_markdown(token):
         # leading whitespace in a list item is already trimmed off by markdown-it
-        return (
-            token.content.startswith("[ ] ")
-            or token.content.startswith("[x] ")
-            or token.content.startswith("[X] ")
-        )
+        return re.match(rf"\[[ xX]]{_GFM_WHITESPACE_RE}+", token.content)
diff --git a/tests/fixtures/tasklists.md b/tests/fixtures/tasklists.md
index 51adafd..dec0fef 100644
--- a/tests/fixtures/tasklists.md
+++ b/tests/fixtures/tasklists.md
@@ -107,3 +107,25 @@ oedered.md:
 </ol>
 
 .
+
+Tab after task list item marker
+.
++ [x]	item 1
++ [ ]		item 2
+.
+<ul class="contains-task-list">
+<li class="task-list-item">	item 1</li>
+<li class="task-list-item">		item 2</li>
+</ul>
+.
+
+Form feed after task list item marker
+.
++ [x]item 1
++ [ ]item 2
+.
+<ul class="contains-task-list">
+<li class="task-list-item">item 1</li>
+<li class="task-list-item">item 2</li>
+</ul>
+.