diff --git a/.circleci/config.yml b/.circleci/config.yml
deleted file mode 100644
index a0213db..0000000
--- a/.circleci/config.yml
+++ /dev/null
@@ -1,27 +0,0 @@
-# Python CircleCI 2.0 configuration file
-#
-# Check https://circleci.com/docs/2.0/language-python/ for more details
-#
-version: 2
-jobs:
-  build:
-    docker:
-      - image: circleci/python:3.6.1
-
-    working_directory: ~/SixtyPical
-
-    steps:
-      - checkout
-
-      - run:
-          name: install dependencies
-          command: |
-            echo "hi"
-            git clone https://github.com/catseye/Falderal
-            git clone https://github.com/catseye/dcc6502
-            (cd dcc6502 && make)
-
-      - run:
-          name: run tests
-          command: |
-            PATH=dcc6502:Falderal/bin:$PATH ./test.sh
diff --git a/.gitignore b/.gitignore
index fa9d82d..e5e98a1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 *.pyc
+__pycache__
 vicerc
diff --git a/HISTORY.md b/HISTORY.md
index 48ea5db..11229b1 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -1,6 +1,14 @@
 History of SixtyPical
 =====================
 
+0.21-2023.0309
+--------------
+
+*   Python 3 is the default interpreter for `sixtypical`.
+*   Test appliance added for testing under Python 2.7.
+*   `dcc6502` test adapter made runnable under both
+    Python 2 and Python 3.
+
 0.21
 ----
 
diff --git a/bin/sixtypical b/bin/sixtypical
index 2296ac3..ad94be2 100755
--- a/bin/sixtypical
+++ b/bin/sixtypical
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 from os.path import realpath, dirname, join
 import sys
diff --git a/test.sh b/test.sh
index 9967a0b..03d6bae 100755
--- a/test.sh
+++ b/test.sh
@@ -2,6 +2,8 @@
 
 # This currently represents a lot of tests!  If you only want to run a subset,
 # it's probably best to run `falderal` manually on the file(s) you want to test.
+# Note also that the `sixtypical-py2.7.md` appliance, in the same directory as
+# `sixtypical.md`, can be used to run the tests under Python 2.7.
 
 falderal --substring-error \
     "tests/appliances/sixtypical.md" \
diff --git a/tests/appliances/bin/dcc6502-adapter b/tests/appliances/bin/dcc6502-adapter
index 85b6f17..f1d2acd 100755
--- a/tests/appliances/bin/dcc6502-adapter
+++ b/tests/appliances/bin/dcc6502-adapter
@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 
 # script that allows the binary output of sixtypical --output-format=c64-basic-prg --compile to be
 # disassembled by https://github.com/tcarmelveilleux/dcc6502
@@ -8,7 +8,10 @@ import re
 from subprocess import check_output
 from tempfile import NamedTemporaryFile
 
-bytes = sys.stdin.read()
+try:
+    bytes = sys.stdin.buffer.read()
+except AttributeError:
+    bytes = sys.stdin.read()
 
 bytes = bytes[14:]
 
@@ -17,6 +20,8 @@ filename = f.name
 f.write(bytes)
 f.close()
 
-lines = [line for line in check_output("dcc6502 -o 2061 {}".format(filename), shell=True).split('\n') if line and not line.startswith(';')]
+output = check_output("dcc6502 -o 2061 {}".format(filename), shell=True)
+output_lines = output.decode('utf-8').split('\n')
+lines = [line for line in output_lines if line and not line.startswith(';')]
 lines = [re.sub(r'\s*\;.*$', '', line) for line in lines]
 sys.stdout.write('\n'.join(lines))
diff --git a/tests/appliances/sixtypical-py2.7.md b/tests/appliances/sixtypical-py2.7.md
new file mode 100644
index 0000000..83f7611
--- /dev/null
+++ b/tests/appliances/sixtypical-py2.7.md
@@ -0,0 +1,30 @@
+This file contains only the [Falderal][] directives that define the different
+functionalities tested by the test suite, assuming that it's the reference
+implementation, `sixtypical`, that is going to implement these functionalities,
+and additionally that `sixtypical` is running under Python 2.7.
+
+NOTE that this is not well-supported anymore, given that Python 2.7 is past
+end-of-life.
+
+[Falderal]:     http://catseye.tc/node/Falderal
+
+    -> Functionality "Check syntax of SixtyPical program" is implemented by
+    -> shell command "python2.7 bin/sixtypical --parse-only --traceback %(test-body-file) && echo ok"
+
+    -> Functionality "Analyze SixtyPical program" is implemented by
+    -> shell command "python2.7 bin/sixtypical --analyze-only --traceback %(test-body-file) && echo ok"
+
+    -> Functionality "Compile SixtyPical program" is implemented by
+    -> shell command "python2.7 bin/sixtypical --output-format=c64-basic-prg --traceback %(test-body-file) --output /tmp/foo && python2.7 tests/appliances/bin/dcc6502-adapter </tmp/foo"
+
+    -> Functionality "Dump callgraph info for SixtyPical program" is implemented by
+    -> shell command "python2.7 bin/sixtypical --dump-callgraph --analyze-only --traceback %(test-body-file)"
+
+    -> Functionality "Compile SixtyPical program with unreachable routine removal" is implemented by
+    -> shell command "python2.7 bin/sixtypical --output-format=c64-basic-prg --prune-unreachable-routines --traceback %(test-body-file) --output /tmp/foo && python2.7 tests/appliances/bin/dcc6502-adapter </tmp/foo"
+
+    -> Functionality "Dump fallthru info for SixtyPical program" is implemented by
+    -> shell command "python2.7 bin/sixtypical --optimize-fallthru --dump-fallthru-info --analyze-only --traceback %(test-body-file)"
+
+    -> Functionality "Compile SixtyPical program with fallthru optimization" is implemented by
+    -> shell command "python2.7 bin/sixtypical --output-format=c64-basic-prg --optimize-fallthru --traceback %(test-body-file) --output /tmp/foo && python2.7 tests/appliances/bin/dcc6502-adapter </tmp/foo"