diff --git a/client/test/player_test.gd b/client/test/player_test.gd
index 8a4fc76..3d85653 100644
--- a/client/test/player_test.gd
+++ b/client/test/player_test.gd
@@ -70,9 +70,10 @@ func test_idle_support_is_stable_on_flat_floor_without_wall_contacts() -> void:
 
 func test_idle_support_is_stable_false_when_floor_is_not_flat_enough() -> void:
 	var slide_normals: Array[Vector3] = [Vector3.UP]
-	var stable: bool = PLAYER_SCRIPT.idle_support_is_stable(
-		true, Vector3(0.02, 0.995, 0.0).normalized(), slide_normals, 0
-	)
+	# Must have floor_normal.dot(UP) < STABLE_IDLE_FLOOR_MIN_UP_DOT (0.999).
+	# (0.02, 0.995).normalized() dots ~0.9998 and incorrectly passes as "flat" at 0.999.
+	var tilted_floor: Vector3 = Vector3(0.05, 0.99875, 0.0).normalized()
+	var stable: bool = PLAYER_SCRIPT.idle_support_is_stable(true, tilted_floor, slide_normals, 0)
 	assert_that(stable).is_false()