diff --git a/spine-cpp/spine-cpp/include/spine/SlotTimeline.h b/spine-cpp/spine-cpp/include/spine/SlotTimeline.h
index f1b0c4023..813e6e355 100644
--- a/spine-cpp/spine-cpp/include/spine/SlotTimeline.h
+++ b/spine-cpp/spine-cpp/include/spine/SlotTimeline.h
@@ -31,16 +31,24 @@
 #define Spine_SlotTimeline_h
 
 #include <spine/dll.h>
+#include <spine/RTTI.h>
 
 namespace spine {
 
 	/// An interface for timelines which change the property of a slot.
 	class SP_API SlotTimeline {
+		RTTI_DECL
+
 	public:
 		virtual ~SlotTimeline() {}
 
 		/// The index of the slot in Skeleton::getSlots() that will be changed when this timeline is applied.
-		virtual int getSlotIndex() = 0;
+		virtual int getSlotIndex();
+
+		virtual void setSlotIndex(int inValue);
+
+	protected:
+		int _slotIndex;
 	};
 }
 
diff --git a/spine-cpp/spine-cpp/src/spine/SlotTimeline.cpp b/spine-cpp/spine-cpp/src/spine/SlotTimeline.cpp
new file mode 100644
index 000000000..b2447f916
--- /dev/null
+++ b/spine-cpp/spine-cpp/src/spine/SlotTimeline.cpp
@@ -0,0 +1,42 @@
+/******************************************************************************
+ * Spine Runtimes License Agreement
+ * Last updated April 5, 2025. Replaces all prior versions.
+ *
+ * Copyright (c) 2013-2025, Esoteric Software LLC
+ *
+ * Integration of the Spine Runtimes into software or otherwise creating
+ * derivative works of the Spine Runtimes is permitted under the terms and
+ * conditions of Section 2 of the Spine Editor License Agreement:
+ * http://esotericsoftware.com/spine-editor-license
+ *
+ * Otherwise, it is permitted to integrate the Spine Runtimes into software
+ * or otherwise create derivative works of the Spine Runtimes (collectively,
+ * "Products"), provided that each user of the Products must obtain their own
+ * Spine Editor license and redistribution of the Products in any form must
+ * include this license and copyright notice.
+ *
+ * THE SPINE RUNTIMES ARE PROVIDED BY ESOTERIC SOFTWARE LLC "AS IS" AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL ESOTERIC SOFTWARE LLC BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES,
+ * BUSINESS INTERRUPTION, OR LOSS OF USE, DATA, OR PROFITS) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THE SPINE RUNTIMES, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *****************************************************************************/
+
+#include <spine/SlotTimeline.h>
+
+using namespace spine;
+
+RTTI_IMPL_NOPARENT(SlotTimeline)
+
+int SlotTimeline::getSlotIndex() {
+	return _slotIndex;
+}
+
+void SlotTimeline::setSlotIndex(int inValue) {
+	_slotIndex = inValue;
+}
\ No newline at end of file