diff --git a/exceptions.py b/exceptions.py
index 81ace96eaa7..6095c88c6a6 100644
--- a/exceptions.py
+++ b/exceptions.py
@@ -40,6 +40,9 @@ def error_location(self):
             return [self.arguments['line_number']]
         return None
 
+    def __str__(self):
+        return f'{self.error_code} {repr(self.arguments)}'
+
 
 class WarningException(HedyException):
     """Fixed That For You warning/exception.
diff --git a/hedy.py b/hedy.py
index cc81fcfa4d9..f769b77e529 100644
--- a/hedy.py
+++ b/hedy.py
@@ -3612,6 +3612,8 @@ def get_parser(level, lang="en", keep_all_tokens=False, skip_faulty=False):
         grammar,
         str(sys.version_info[:2]),
         str(parser_opts),
+        # When we upgrade Lark, make sure to not load cached parsers from old versions
+        str(lark.__version__),
     )).encode()).hexdigest()
 
     cached_parser_file = f"cached-parser-{level}-{lang}-{unique_parser_hash}.pkl"
diff --git a/requirements.txt b/requirements.txt
index e578f0e0a21..c2ecb0f89d7 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,8 @@
 Flask==3.0.2
 Werkzeug==3.0.6
-lark==1.1.1
+# We cannot go higher than this, because starting 1.2.1+
+# we parse "100" as text instead of a number.
+lark==1.1.9
 gunicorn==22.0.0
 flask-compress==1.4.0
 requests==2.32.0
@@ -10,7 +12,7 @@ boto3>=1.16.50
 MarkupSafe==2.1.2
 ruamel.yaml==0.18.6
 docopt==0.6.2
-pydantic==1.10.13
+pydantic==1.10.21
 lazy==1.4
 PySumTypes==0.0.1
 beautifulsoup4==4.9.3