diff --git a/CHANGELOG.md b/CHANGELOG.md
index e35fb679..4869a170 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,11 +2,12 @@
 
 All notable changes to this project will be documented in this file. The format is based on [Keep a Changelog](http://keepachangelog.com/).
 
-## [0.5.29] - [unreleased]
+## [0.6.0] - [unreleased]
 ### Added
 - Add `utils.merge_bboxes(bboxes)`, which returns the smallest bounding box that contains all bounding boxes in the `bboxes` argument.
 
 ## Changed
+- Upgrade `pdfminer.six` from `20200517` to `20211012`; see [that library's changelog](https://github.com/pdfminer/pdfminer.six/blob/develop/CHANGELOG.md) for details, but a key difference is an improvement in how it assigns `line`, `rect`, and `curve` objects. (Diagonal two-point lines, for instance, are now `line` objects instead of `curve` objects.)
 - Change behavior of horizontal `text_strategy`, so that it uses the top and bottom of *every* word, not just the top of every word and the bottom of the last. ([#467](https://github.com/jsvine/pdfplumber/pull/467) + [#466](https://github.com/jsvine/pdfplumber/issues/466) + [#265](https://github.com/jsvine/pdfplumber/issues/265)) [h/t @bobluda + @samkit-jain]
 
 ### Fixed
diff --git a/requirements.txt b/requirements.txt
index 20779c53..ff3250e4 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,3 @@
-pdfminer.six==20200517
+pdfminer.six==20211012
 Pillow>=7.0.0
 Wand
diff --git a/tests/test_convert.py b/tests/test_convert.py
index be09d759..8b64e6f4 100644
--- a/tests/test_convert.py
+++ b/tests/test_convert.py
@@ -55,7 +55,7 @@ def test_additional_attr_types(self):
 
     def test_csv(self):
         c = self.pdf.to_csv()
-        assert c.split("\r\n")[2] == (
+        assert c.split("\r\n")[9] == (
             "char,1,45.83,58.826,656.82,674.82,117.18,117.18,135.18,12.996,"
             '18.0,12.996,,,,,,TimesNewRomanPSMT,,,,"(0, 0, 0)",,,18.0,,,,,Y,,1,'
         )
@@ -68,7 +68,7 @@ def test_csv(self):
 
     def test_csv_all_types(self):
         c = self.pdf.to_csv(types=None)
-        assert c.split("\r\n")[1].split(",")[0] == "curve"
+        assert c.split("\r\n")[1].split(",")[0] == "line"
 
     def test_cli(self):
         res = run(
diff --git a/tests/test_issues.py b/tests/test_issues.py
index e143c391..d04d8522 100644
--- a/tests/test_issues.py
+++ b/tests/test_issues.py
@@ -38,7 +38,7 @@ def filter_rects(rects):
                     rects_found.append(rect)
             return rects_found
 
-        def determine_if_checked(checkbox, curve_list):
+        def determine_if_checked(checkbox, checklines):
             """
             This figures out if the bounding box of (either) line used to make
             one half of the 'x' is the right size and overlaps with a rectangle.
@@ -49,7 +49,7 @@ def determine_if_checked(checkbox, curve_list):
             But here we only test there's at least one.
             """
 
-            for curve in curve_list:
+            for cl in checklines:
 
                 if (
                     checkbox["height"] > (RECT_HEIGHT - RECT_TOLERANCE)
@@ -61,13 +61,9 @@ def determine_if_checked(checkbox, curve_list):
                     xmatch = False
                     ymatch = False
 
-                    if max(checkbox["x0"], curve["x0"]) <= min(
-                        checkbox["x1"], curve["x1"]
-                    ):
+                    if max(checkbox["x0"], cl["x0"]) <= min(checkbox["x1"], cl["x1"]):
                         xmatch = True
-                    if max(checkbox["y0"], curve["y0"]) <= min(
-                        checkbox["y1"], curve["y1"]
-                    ):
+                    if max(checkbox["y0"], cl["y0"]) <= min(checkbox["y1"], cl["y1"]):
                         ymatch = True
                     if xmatch and ymatch:
                         return True
@@ -75,10 +71,12 @@ def determine_if_checked(checkbox, curve_list):
             return False
 
         p0 = pdf.pages[0]
-        curves = p0.objects["curve"]
+        checklines = [
+            line for line in p0.lines if line["height"] == line["width"]
+        ]  # These are diagonals
         rects = filter_rects(p0.objects["rect"])
 
-        n_checked = sum([determine_if_checked(rect, curves) for rect in rects])
+        n_checked = sum([determine_if_checked(rect, checklines) for rect in rects])
 
         assert n_checked == 5
         pdf.close()