diff --git a/tests/test_workout_constants.py b/tests/test_workout_constants.py
new file mode 100644
index 0000000..2ecc5e1
--- /dev/null
+++ b/tests/test_workout_constants.py
@@ -0,0 +1,49 @@
+"""Regression tests pinning workout constant IDs to Garmin API values.
+
+Prevents silent drift of constant values (see issue #333).
+"""
+
+from garminconnect.workout import ConditionType, SportType, StepType, TargetType
+
+
+def test_target_type_ids():
+    """Pin TargetType IDs to match Garmin API values (issue #333)."""
+    assert TargetType.NO_TARGET == 1
+    assert TargetType.POWER == 2
+    assert TargetType.CADENCE == 3
+    assert TargetType.HEART_RATE == 4
+    assert TargetType.SPEED == 5
+    assert TargetType.OPEN == 6
+
+
+def test_step_type_ids():
+    """Pin StepType IDs to match Garmin API values."""
+    assert StepType.WARMUP == 1
+    assert StepType.COOLDOWN == 2
+    assert StepType.INTERVAL == 3
+    assert StepType.RECOVERY == 4
+    assert StepType.REST == 5
+    assert StepType.REPEAT == 6
+
+
+def test_condition_type_ids():
+    """Pin ConditionType IDs to match Garmin API values."""
+    assert ConditionType.DISTANCE == 1
+    assert ConditionType.TIME == 2
+    assert ConditionType.HEART_RATE == 3
+    assert ConditionType.CALORIES == 4
+    assert ConditionType.CADENCE == 5
+    assert ConditionType.POWER == 6
+    assert ConditionType.ITERATIONS == 7
+
+
+def test_sport_type_ids():
+    """Pin SportType IDs to match Garmin API values."""
+    assert SportType.RUNNING == 1
+    assert SportType.CYCLING == 2
+    assert SportType.SWIMMING == 3
+    assert SportType.WALKING == 4
+    assert SportType.MULTI_SPORT == 5
+    assert SportType.FITNESS_EQUIPMENT == 6
+    assert SportType.HIKING == 7
+    assert SportType.OTHER == 8