diff --git a/mercurial/minirst.py b/mercurial/minirst.py
--- a/mercurial/minirst.py
+++ b/mercurial/minirst.py
@@ -225,6 +225,8 @@ def prunecontainers(blocks, keep):
     return blocks, pruned
 
 
+_sectionre = re.compile(r"""^([-=`:.'"~^_*+#])\1+$""")
+
 def findsections(blocks):
     """Finds sections.
 
@@ -240,7 +242,8 @@ def findsections(blocks):
         # +------------------------------+
         if (block['type'] == 'paragraph' and
             len(block['lines']) == 2 and
-            block['lines'][1] == '-' * len(block['lines'][0])):
+            len(block['lines'][0]) == len(block['lines'][1]) and
+            _sectionre.match(block['lines'][1])):
             block['underline'] = block['lines'][1][0]
             block['type'] = 'section'
             del block['lines'][1]
diff --git a/tests/test-minirst.py b/tests/test-minirst.py
--- a/tests/test-minirst.py
+++ b/tests/test-minirst.py
@@ -184,8 +184,14 @@ debugformat('roles', roles, 60)
 
 
 sections = """
-A Somewhat Wide Section Header
-------------------------------
+Title
+=====
+
+Section
+-------
+
+Subsection
+''''''''''
 
 Markup: ``foo`` and :hg:`help`
 ------------------------------
diff --git a/tests/test-minirst.py.out b/tests/test-minirst.py.out
--- a/tests/test-minirst.py.out
+++ b/tests/test-minirst.py.out
@@ -305,8 +305,14 @@ Please see "hg add".
 
 sections formatted to fit within 20 characters:
 ----------------------------------------------------------------------
-A Somewhat Wide Section Header
-------------------------------
+Title
+=====
+
+Section
+-------
+
+Subsection
+''''''''''
 
 Markup: "foo" and "hg help"
 ---------------------------