diff --git a/requirements.txt b/requirements.txt
index b792703..e4fa01b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,7 +1,11 @@
 # python 3.8.7
 
 flask==1.1.2
-flask-sqlalchemy==2.4.4
+# NOTE: Newer versions of SQLAlchemy contain a change that breaks Flask-SQLALchemy :-/
+#   https://stackoverflow.com/a/66652728
+# This wasn't a problem on vm-linux-dev, but manifested itself on the rPi4 (probably because
+# the virtualenv on vm-linux-dev was built before this became a problem).
+flask-sqlalchemy==2.5.1
 psycopg2-binary==2.8.6
 alembic==1.4.3
 pyyaml==5.3.1