diff --git a/djhtml/__main__.py b/djhtml/__main__.py
index c346b3b..ffb693f 100644
--- a/djhtml/__main__.py
+++ b/djhtml/__main__.py
@@ -71,7 +71,9 @@ def main():
 
         # Indent input file
         try:
-            result = Mode(source).indent(options.tabwidth or guess or 4)
+            result = Mode(source, extra_blocks=options.extra_block).indent(
+                options.tabwidth or guess or 4
+            )
         except modes.MaxLineLengthExceeded:
             problematic_files += 1
             _error(f"Maximum line length exceeded in {filename}")
diff --git a/djhtml/modes.py b/djhtml/modes.py
index d017da3..5f6238e 100644
--- a/djhtml/modes.py
+++ b/djhtml/modes.py
@@ -12,7 +12,7 @@ class BaseMode:
 
     MAX_LINE_LENGTH = 10_000
 
-    def __init__(self, source=None, return_mode=None):
+    def __init__(self, source=None, return_mode=None, extra_blocks=None):
         """
         Instantiate with source text before calling indent(), or
         with the return_mode when invoked from within another mode.
@@ -24,6 +24,7 @@ def __init__(self, source=None, return_mode=None):
         self.source = source
         self.return_mode = return_mode or self
         self.token_re = compile_re(self.RAW_TOKENS)
+        self.extra_blocks = dict(extra_blocks or [])
 
         # To keep track of the current and previous offsets.
         self.offsets = dict(relative=0, absolute=0)
@@ -241,6 +242,9 @@ def create_token(self, raw_token, src, line):
         return token, mode
 
     def _has_closing_token(self, name, raw_token, src):
+        endtag = self.extra_blocks.get(name)
+        if endtag:
+            return re.search(f"{{%[-+]? *{endtag}(?: .*?|)%}}", src)
         if not re.search(f"{{%[-+]? *(end_?|/){name}(?: .*?|)%}}", src):
             return False
         if regex := self.AMBIGUOUS_BLOCK_TAGS.get(name):
@@ -406,6 +410,7 @@ def __init__(self, *args, **kwargs):
         self.haskell_re = re.compile(r"^ *, ([$\w-]+ *=|[$\w-]+;?)")
         self.variable_re = re.compile(r"^ *([$\w-]+ *=|[$\w-]+;?)")
         self.previous_line_ended_with_comma = False
+        self.extra_blocks = {}
 
     def create_token(self, raw_token, src, line):
         mode = self
@@ -513,6 +518,7 @@ def __init__(self, endtag, *, mode, return_mode):
         self.mode = mode
         self.return_mode = return_mode
         self.token_re = compile_re([r"\n", endtag])
+        self.extra_blocks = {}
 
     def create_token(self, raw_token, src, line):
         if re.match(self.endtag, raw_token):
@@ -536,6 +542,7 @@ def __init__(self, tagname, line, return_mode, absolute, offsets):
         self.token_re = compile_re(self.RAW_TOKENS)
         self.inside_attr = False
         self.additional_offset = -len(tagname) - 1 if absolute else 0
+        self.extra_blocks = {}
 
     def create_token(self, raw_token, src, line):
         mode = self
diff --git a/djhtml/options.py b/djhtml/options.py
index 3d05b85..831f9b0 100644
--- a/djhtml/options.py
+++ b/djhtml/options.py
@@ -58,6 +58,13 @@
 )
 parser.add_argument("-d", "--debug", action="store_true", help=argparse.SUPPRESS)
 parser.add_argument("-i", "--in-place", action="store_true", help=argparse.SUPPRESS)
+parser.add_argument(
+    "-b",
+    "--extra-block",
+    action="append",
+    help="startblock,endblock pair",
+    type=lambda x: tuple(x.split(",")),
+)
 
 # Parse arguments and assign attributes to self
 self = sys.modules[__name__]
diff --git a/tests/suite/django.html b/tests/suite/django.html
index bea3af6..73da8db 100644
--- a/tests/suite/django.html
+++ b/tests/suite/django.html
@@ -195,3 +195,8 @@ <h1>Welcome, {{ request.user }}</h1>
 {% customtag %}
     <div></div>
 {% endcustomtag %}
+
+<!-- Custom tag with custom end tag -->
+{% weird_tag %}
+    <div></div>
+{% endweird %}
diff --git a/tests/suite/django.tokens b/tests/suite/django.tokens
index 21112ac..2c2d4e6 100644
--- a/tests/suite/django.tokens
+++ b/tests/suite/django.tokens
@@ -195,4 +195,9 @@ Line([Open('<!--', mode=DjHTML, ignore=True), Text(' Custom tag ', mode=Comment,
 Line([Open('{% customtag %}', mode=DjTXT)])
 Line([Text('    ', mode=DjHTML), Text('<', mode=DjHTML), Text('div', mode=InsideHTMLTag, absolute=5), Open('>', mode=DjHTML, level=1), Close('</div>', mode=DjHTML)], level=1)
 Line([Close('{% endcustomtag %}', mode=DjTXT)])
+Line([])
+Line([Open('<!--', mode=DjHTML, ignore=True), Text(' Custom tag with custom end tag ', mode=Comment, ignore=True), Close('-->', mode=DjHTML, ignore=True)], ignore=True)
+Line([Open('{% weird_tag %}', mode=DjTXT)])
+Line([Text('    ', mode=DjHTML), Text('<', mode=DjHTML), Text('div', mode=InsideHTMLTag, absolute=5), Open('>', mode=DjHTML, level=1), Close('</div>', mode=DjHTML)], level=1)
+Line([Close('{% endweird %}', mode=DjTXT)])
 Line([])
\ No newline at end of file
diff --git a/tests/test_suite.py b/tests/test_suite.py
index e7a5c1e..ce4fa73 100644
--- a/tests/test_suite.py
+++ b/tests/test_suite.py
@@ -27,13 +27,19 @@ def _test_file(self, basename):
             expected_tokens = f.read()
 
         # Indent the expected output to 0 (no indentation)
-        unindented = DjHTML(expected_output).indent(0)
+        unindented = DjHTML(
+            expected_output, extra_blocks=[("weird_tag", "endweird")]
+        ).indent(0)
         self.assertNotEqual(unindented, expected_output)
 
         # Re-indent the unindented output to 4
-        actual_output = DjHTML(unindented).indent(4)
+        actual_output = DjHTML(
+            unindented, extra_blocks=[("weird_tag", "endweird")]
+        ).indent(4)
         self.assertEqual(expected_output, actual_output)
 
         # Compare the tokenization
-        actual_tokens = DjHTML(actual_output).debug()
+        actual_tokens = DjHTML(
+            actual_output, extra_blocks=[("weird_tag", "endweird")]
+        ).debug()
         self.assertEqual(expected_tokens, actual_tokens)