diff --git a/src/calibre/ebooks/epub/cfi/parse.py b/src/calibre/ebooks/epub/cfi/parse.py
index e3ddc41de2..a3fd308e1e 100644
--- a/src/calibre/ebooks/epub/cfi/parse.py
+++ b/src/calibre/ebooks/epub/cfi/parse.py
@@ -26,7 +26,7 @@ class Parser:
         # No leading zeros allowed for integers
         integer = r'(?:[1-9][0-9]*)|0'
         # No leading zeros, except for numbers in (0, 1) and no trailing zeros for the fractional part
-        frac = r'\.[0-9]*[1-9]'
+        frac = r'\.[0-9]{1,}'
         number = r'(?:[1-9][0-9]*(?:{0})?)|(?:0{0})|(?:0)'.format(frac)
         def c(x):
             return regex.compile(x, flags=regex.VERSION1)
@@ -239,3 +239,8 @@ def decode_cfi(root, cfi):
         else:
             return
     return ans
+
+
+if __name__ == '__main__':
+    import sys
+    print(cfi_sort_key(sys.argv[-1], only_path=False))
diff --git a/src/calibre/ebooks/epub/cfi/tests.py b/src/calibre/ebooks/epub/cfi/tests.py
index cc04fb8a4a..71547176fa 100644
--- a/src/calibre/ebooks/epub/cfi/tests.py
+++ b/src/calibre/ebooks/epub/cfi/tests.py
@@ -79,6 +79,7 @@ class Tests(unittest.TestCase):
             ('/1~0.01', o('~', 0.01), ''),
             ('/1~1.301', o('~', 1.301), ''),
             ('/1@23:34.1', o('@', (23, 34.1)), ''),
+            ('/1@23:34.10', o('@', (23, 34.1)), ''),
             ('/1~3@3.1:2.3', o('~', 3.0, '@', (3.1, 2.3)), ''),
             ('/1:0', o(':', 0), ''),
             ('/1:3', o(':', 3), ''),