diff --git a/CHANGES.md b/CHANGES.md
index e1c9c958..0ebf4ea7 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -7,6 +7,7 @@
 - [pull #644] Fix a number of em/strong issues (#641, #642, #643)
 - [pull #659] Fix a number of safemode issues (#647)
 - [pull #665] Rewrite emphasis and strong processing to be more GFM compliant
+- [pull #672] Fix nested footnote references (#664)
 
 
 ## python-markdown2 2.5.4
diff --git a/lib/markdown2.py b/lib/markdown2.py
index 68dced73..9364550a 100755
--- a/lib/markdown2.py
+++ b/lib/markdown2.py
@@ -514,12 +514,7 @@ def convert(self, text: str) -> 'UnicodeWithAttrs':
         text = self._run_block_gamut(text)
 
         if "footnotes" in self.extras:
-            def footnote_sub(match):
-                normed_id = match.group(1)
-                self.footnote_ids.append(normed_id)
-                return str(len(self.footnote_ids))
-
-            text = re.sub(r'%s-(.*?)(?=</a></sup>)' % self._footnote_marker, footnote_sub, text)
+            text = self._do_footnote_marker(text)
             text = self._add_footnotes(text)
 
         text = self.postprocess(text)
@@ -572,6 +567,15 @@ def toc_sort(entry):
             rv.metadata = self.metadata
         return rv
 
+    def _do_footnote_marker(self, text):
+        def footnote_sub(match):
+            normed_id = match.group(1)
+            if normed_id not in self.footnote_ids:
+                self.footnote_ids.append(normed_id)
+            return str(len(self.footnote_ids))
+
+        return re.sub(r'%s-(.*?)(?=</a></sup>)' % self._footnote_marker, footnote_sub, text)
+
     @mark_stage(Stage.POSTPROCESS)
     def postprocess(self, text: str) -> str:
         """A hook for subclasses to do some postprocessing of the html, if
@@ -2170,7 +2174,12 @@ def _add_footnotes(self, text: str) -> str:
                 if i != 0:
                     footer.append('')
                 footer.append('<li id="fn-%s">' % id)
-                footer.append(self._run_block_gamut(self.footnotes[id]))
+                footer.append(
+                    # handle any nested footnote markers
+                    self._do_footnote_marker(
+                        self._run_block_gamut(self.footnotes[id])
+                    )
+                )
                 try:
                     backlink = ('<a href="#fnref-%s" ' +
                             'class="footnoteBackLink" ' +
diff --git a/test/tm-cases/nested_footnotes_issue664.html b/test/tm-cases/nested_footnotes_issue664.html
new file mode 100644
index 00000000..59492f29
--- /dev/null
+++ b/test/tm-cases/nested_footnotes_issue664.html
@@ -0,0 +1,14 @@
+<p>foo<sup class="footnote-ref" id="fnref-n1"><a href="#fn-n1">1</a></sup></p>
+
+<div class="footnotes">
+<hr />
+<ol>
+<li id="fn-n1">
+<p>Note 1<sup class="footnote-ref" id="fnref-n2"><a href="#fn-n2">2</a></sup>&#160;<a href="#fnref-n1" class="footnoteBackLink" title="Jump back to footnote 1 in the text.">&#8617;</a></p>
+</li>
+
+<li id="fn-n2">
+<p>Note 2&#160;<a href="#fnref-n2" class="footnoteBackLink" title="Jump back to footnote 2 in the text.">&#8617;</a></p>
+</li>
+</ol>
+</div>
diff --git a/test/tm-cases/nested_footnotes_issue664.opts b/test/tm-cases/nested_footnotes_issue664.opts
new file mode 100644
index 00000000..9c801570
--- /dev/null
+++ b/test/tm-cases/nested_footnotes_issue664.opts
@@ -0,0 +1 @@
+{"extras": ["footnotes"]}
\ No newline at end of file
diff --git a/test/tm-cases/nested_footnotes_issue664.text b/test/tm-cases/nested_footnotes_issue664.text
new file mode 100644
index 00000000..b6b644a4
--- /dev/null
+++ b/test/tm-cases/nested_footnotes_issue664.text
@@ -0,0 +1,4 @@
+foo[^n1]
+
+[^n1]: Note 1[^n2]
+[^n2]: Note 2
\ No newline at end of file