diff --git a/aw_transform/classify.py b/aw_transform/classify.py
index 898f416..b0c573b 100644
--- a/aw_transform/classify.py
+++ b/aw_transform/classify.py
@@ -1,3 +1,4 @@
+import logging
 from typing import Pattern, List, Iterable, Tuple, Dict, Optional, Any
 from functools import reduce
 import re
@@ -5,6 +6,8 @@
 from aw_core import Event
 
 
+logger = logging.getLogger(__name__)
+
 Tag = str
 Category = List[str]
 
@@ -20,13 +23,24 @@ def __init__(self, rules: Dict[str, Any]) -> None:
 
         # NOTE: Also checks that the regex isn't an empty string (which would erroneously match everything)
         regex_str = rules.get("regex", None)
-        self.regex = (
-            re.compile(
-                regex_str, (re.IGNORECASE if self.ignore_case else 0) | re.UNICODE
-            )
-            if regex_str
-            else None
-        )
+        if regex_str:
+            try:
+                self.regex = re.compile(
+                    regex_str,
+                    (re.IGNORECASE if self.ignore_case else 0) | re.UNICODE,
+                )
+            except re.error as e:
+                # An invalid user-supplied pattern should not crash categorization
+                # for the entire query. Log it and disable this rule (match nothing).
+                logger.warning(
+                    "Invalid regex pattern %r in category/tag rule (%s); "
+                    "this rule will match nothing.",
+                    regex_str,
+                    e,
+                )
+                self.regex = None
+        else:
+            self.regex = None
 
     def match(self, e: Event) -> bool:
         if self.select_keys:
diff --git a/tests/test_transforms.py b/tests/test_transforms.py
index df627db..3b3b27e 100644
--- a/tests/test_transforms.py
+++ b/tests/test_transforms.py
@@ -435,6 +435,35 @@ def test_tags():
     assert len(events[1].data["$tags"]) == 0
 
 
+def test_rule_invalid_regex_does_not_raise():
+    # An invalid user-supplied pattern (e.g. "Notepad++" on Python versions
+    # where "++" is not a valid quantifier) must not raise from Rule.__init__.
+    # Instead the rule should silently disable itself. See:
+    # https://github.com/ActivityWatch/activitywatch/issues/1340
+    rule = Rule({"regex": "*invalid("})
+    assert rule.regex is None
+
+    now = datetime.now(timezone.utc)
+    e = Event(timestamp=now, duration=0, data={"key": "anything"})
+    assert rule.match(e) is False
+
+
+def test_categorize_survives_invalid_regex():
+    # A single bad rule should not break categorization for the rest.
+    now = datetime.now(timezone.utc)
+    classes = [
+        (["Bad"], Rule({"regex": "*invalid("})),
+        (["Test"], Rule({"regex": "^just"})),
+    ]
+    events = [
+        Event(timestamp=now, duration=0, data={"key": "just a test"}),
+        Event(timestamp=now, duration=0, data={"key": "unrelated"}),
+    ]
+    events = categorize(events, classes)
+    assert events[0].data["$category"] == ["Test"]
+    assert events[1].data["$category"] == ["Uncategorized"]
+
+
 def test_union_no_overlap():
     from pprint import pprint