diff --git a/spine-cpp/spine-cpp/include/spine/PhysicsConstraintTimeline.h b/spine-cpp/spine-cpp/include/spine/PhysicsConstraintTimeline.h
index e0dccb4b3..67a9a8657 100644
--- a/spine-cpp/spine-cpp/include/spine/PhysicsConstraintTimeline.h
+++ b/spine-cpp/spine-cpp/include/spine/PhysicsConstraintTimeline.h
@@ -86,6 +86,7 @@ namespace spine {
         }
     };
 
+    /// Changes a physics constraint's PhysicsConstraintPose::getStrength().
     class SP_API PhysicsConstraintStrengthTimeline : public PhysicsConstraintTimeline {
         friend class SkeletonBinary;