diff --git a/include/slang-rhi.h b/include/slang-rhi.h
index 6518100e..4d52a5bd 100644
--- a/include/slang-rhi.h
+++ b/include/slang-rhi.h
@@ -257,6 +257,12 @@ enum class Format
     _Count,
 };
 
+enum class IndexFormat
+{
+    UInt16,
+    UInt32,
+};
+
 // TODO: Aspect = Color, Depth, Stencil, etc.
 // TODO: Channel = R, G, B, A, D, S, etc.
 // TODO: Pick : pixel or texel
@@ -1656,7 +1662,8 @@ class IRenderCommandEncoder : public ICommandEncoder
         setVertexBuffers(slot, 1, &buffer, &offset);
     }
 
-    virtual SLANG_NO_THROW void SLANG_MCALL setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset = 0) = 0;
+    virtual SLANG_NO_THROW void SLANG_MCALL
+    setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset = 0) = 0;
 
     virtual SLANG_NO_THROW Result SLANG_MCALL draw(GfxCount vertexCount, GfxIndex startVertex = 0) = 0;
 
diff --git a/src/command-writer.h b/src/command-writer.h
index 8ddb8898..9f13a5ec 100644
--- a/src/command-writer.h
+++ b/src/command-writer.h
@@ -235,7 +235,7 @@ class CommandWriter
         ));
     }
 
-    void setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset)
+    void setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset)
     {
         auto bufferOffset = encodeObject(static_cast<Buffer*>(buffer));
         m_commands.push_back(
diff --git a/src/d3d/d3d-util.cpp b/src/d3d/d3d-util.cpp
index 7b7fa278..b6739e45 100644
--- a/src/d3d/d3d-util.cpp
+++ b/src/d3d/d3d-util.cpp
@@ -332,6 +332,19 @@ DXGI_FORMAT D3DUtil::getMapFormat(Format format)
     }
 }
 
+DXGI_FORMAT D3DUtil::getIndexFormat(IndexFormat indexFormat)
+{
+    switch (indexFormat)
+    {
+    case IndexFormat::UInt16:
+        return DXGI_FORMAT_R16_UINT;
+    case IndexFormat::UInt32:
+        return DXGI_FORMAT_R32_UINT;
+    default:
+        return DXGI_FORMAT_UNKNOWN;
+    }
+}
+
 DXGI_FORMAT D3DUtil::calcResourceFormat(UsageType usage, Int usageFlags, DXGI_FORMAT format)
 {
     SLANG_UNUSED(usage);
diff --git a/src/d3d/d3d-util.h b/src/d3d/d3d-util.h
index fdb7a229..db63ae87 100644
--- a/src/d3d/d3d-util.h
+++ b/src/d3d/d3d-util.h
@@ -76,6 +76,8 @@ class D3DUtil
     /// DXGI_FORMAT_UNKNOWN
     static DXGI_FORMAT getMapFormat(Format format);
 
+    static DXGI_FORMAT getIndexFormat(IndexFormat indexFormat);
+
     /// Given the usage, flags, and format will return the most suitable format. Will return DXGI_UNKNOWN if combination
     /// is not possible
     static DXGI_FORMAT calcFormat(UsageType usage, DXGI_FORMAT format);
diff --git a/src/d3d11/d3d11-device.cpp b/src/d3d11/d3d11-device.cpp
index d115ad75..579419e3 100644
--- a/src/d3d11/d3d11-device.cpp
+++ b/src/d3d11/d3d11-device.cpp
@@ -983,9 +983,9 @@ void DeviceImpl::setVertexBuffers(
         ->IASetVertexBuffers((UINT)startSlot, (UINT)slotCount, dxBuffers, &vertexStrides[0], &vertexOffsets[0]);
 }
 
-void DeviceImpl::setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset)
+void DeviceImpl::setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset)
 {
-    DXGI_FORMAT dxFormat = D3DUtil::getMapFormat(indexFormat);
+    DXGI_FORMAT dxFormat = D3DUtil::getIndexFormat(indexFormat);
     m_immediateContext->IASetIndexBuffer(((BufferImpl*)buffer)->m_buffer, dxFormat, UINT(offset));
 }
 
diff --git a/src/d3d11/d3d11-device.h b/src/d3d11/d3d11-device.h
index 708ec944..44d7683c 100644
--- a/src/d3d11/d3d11-device.h
+++ b/src/d3d11/d3d11-device.h
@@ -66,7 +66,7 @@ class DeviceImpl : public ImmediateDevice
         IBuffer* const* buffers,
         const Offset* offsets
     ) override;
-    virtual void setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset) override;
+    virtual void setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset) override;
     virtual void setViewports(GfxCount count, Viewport const* viewports) override;
     virtual void setScissorRects(GfxCount count, ScissorRect const* rects) override;
     virtual void setPipeline(IPipeline* state) override;
diff --git a/src/d3d12/d3d12-command-encoder.cpp b/src/d3d12/d3d12-command-encoder.cpp
index 88d41048..75e731a1 100644
--- a/src/d3d12/d3d12-command-encoder.cpp
+++ b/src/d3d12/d3d12-command-encoder.cpp
@@ -995,10 +995,10 @@ void RenderCommandEncoderImpl::setVertexBuffers(
     }
 }
 
-void RenderCommandEncoderImpl::setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset)
+void RenderCommandEncoderImpl::setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset)
 {
     m_boundIndexBuffer = (BufferImpl*)buffer;
-    m_boundIndexFormat = D3DUtil::getMapFormat(indexFormat);
+    m_boundIndexFormat = D3DUtil::getIndexFormat(indexFormat);
     m_boundIndexOffset = (UINT)offset;
 }
 
diff --git a/src/d3d12/d3d12-command-encoder.h b/src/d3d12/d3d12-command-encoder.h
index 0c014e05..3282c326 100644
--- a/src/d3d12/d3d12-command-encoder.h
+++ b/src/d3d12/d3d12-command-encoder.h
@@ -213,7 +213,7 @@ class RenderCommandEncoderImpl : public IRenderCommandEncoder, public CommandEnc
     setVertexBuffers(GfxIndex startSlot, GfxCount slotCount, IBuffer* const* buffers, const Offset* offsets) override;
 
     virtual SLANG_NO_THROW void SLANG_MCALL
-    setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset = 0) override;
+    setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset = 0) override;
 
     Result prepareDraw();
     virtual SLANG_NO_THROW Result SLANG_MCALL draw(GfxCount vertexCount, GfxIndex startVertex = 0) override;
diff --git a/src/debug-layer/debug-command-encoder.cpp b/src/debug-layer/debug-command-encoder.cpp
index 0eae2f95..84dfb767 100644
--- a/src/debug-layer/debug-command-encoder.cpp
+++ b/src/debug-layer/debug-command-encoder.cpp
@@ -264,7 +264,7 @@ void DebugRenderCommandEncoder::setVertexBuffers(
     baseObject->setVertexBuffers(startSlot, slotCount, innerBuffers.data(), offsets);
 }
 
-void DebugRenderCommandEncoder::setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset)
+void DebugRenderCommandEncoder::setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset)
 {
     SLANG_RHI_API_FUNC;
     auto innerBuffer = static_cast<DebugBuffer*>(buffer)->baseObject.get();
diff --git a/src/debug-layer/debug-command-encoder.h b/src/debug-layer/debug-command-encoder.h
index 19e4e308..298a0abd 100644
--- a/src/debug-layer/debug-command-encoder.h
+++ b/src/debug-layer/debug-command-encoder.h
@@ -159,7 +159,7 @@ class DebugRenderCommandEncoder : public UnownedDebugObject<IRenderCommandEncode
     virtual SLANG_NO_THROW void SLANG_MCALL
     setVertexBuffers(GfxIndex startSlot, GfxCount slotCount, IBuffer* const* buffers, const Offset* offsets) override;
     virtual SLANG_NO_THROW void SLANG_MCALL
-    setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset = 0) override;
+    setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset = 0) override;
     virtual SLANG_NO_THROW Result SLANG_MCALL draw(GfxCount vertexCount, GfxIndex startVertex = 0) override;
     virtual SLANG_NO_THROW Result SLANG_MCALL
     drawIndexed(GfxCount indexCount, GfxIndex startIndex = 0, GfxIndex baseVertex = 0) override;
diff --git a/src/immediate-device.cpp b/src/immediate-device.cpp
index 4115d3ce..f9d3b433 100644
--- a/src/immediate-device.cpp
+++ b/src/immediate-device.cpp
@@ -339,7 +339,7 @@ class CommandBufferImpl : public ICommandBuffer, public ComObject
         }
 
         virtual SLANG_NO_THROW void SLANG_MCALL
-        setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset) override
+        setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset) override
         {
             m_writer->setIndexBuffer(buffer, indexFormat, offset);
         }
@@ -591,7 +591,7 @@ class CommandBufferImpl : public ICommandBuffer, public ComObject
             case CommandName::SetIndexBuffer:
                 m_device->setIndexBuffer(
                     m_writer.getObject<Buffer>(cmd.operands[0]),
-                    (Format)cmd.operands[1],
+                    (IndexFormat)cmd.operands[1],
                     (UInt)cmd.operands[2]
                 );
                 break;
diff --git a/src/immediate-device.h b/src/immediate-device.h
index c97cd7f0..70b1ff6b 100644
--- a/src/immediate-device.h
+++ b/src/immediate-device.h
@@ -60,7 +60,7 @@ class ImmediateDevice : public Device
         IBuffer* const* buffers,
         const Offset* offsets
     ) = 0;
-    virtual void setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset = 0) = 0;
+    virtual void setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset = 0) = 0;
     virtual void draw(GfxCount vertexCount, GfxIndex startVertex = 0) = 0;
     virtual void drawIndexed(GfxCount indexCount, GfxIndex startIndex = 0, GfxIndex baseVertex = 0) = 0;
     virtual void drawInstanced(
@@ -133,7 +133,7 @@ class ImmediateComputeDeviceBase : public ImmediateDevice
         SLANG_UNUSED(buffers);
         SLANG_UNUSED(offsets);
     }
-    virtual void setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset = 0) override
+    virtual void setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset = 0) override
     {
         SLANG_UNUSED(buffer);
         SLANG_UNUSED(indexFormat);
diff --git a/src/metal/metal-command-encoder.cpp b/src/metal/metal-command-encoder.cpp
index 689e485c..081181a4 100644
--- a/src/metal/metal-command-encoder.cpp
+++ b/src/metal/metal-command-encoder.cpp
@@ -389,17 +389,17 @@ void RenderCommandEncoderImpl::setVertexBuffers(
     }
 }
 
-void RenderCommandEncoderImpl::setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset)
+void RenderCommandEncoderImpl::setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset)
 {
     m_indexBuffer = static_cast<BufferImpl*>(buffer)->m_buffer.get();
     m_indexBufferOffset = offset;
 
     switch (indexFormat)
     {
-    case Format::R16_UINT:
+    case IndexFormat::UInt16:
         m_indexBufferType = MTL::IndexTypeUInt16;
         break;
-    case Format::R32_UINT:
+    case IndexFormat::UInt32:
         m_indexBufferType = MTL::IndexTypeUInt32;
         break;
     default:
diff --git a/src/metal/metal-command-encoder.h b/src/metal/metal-command-encoder.h
index a07ad49d..94cc4faf 100644
--- a/src/metal/metal-command-encoder.h
+++ b/src/metal/metal-command-encoder.h
@@ -187,7 +187,7 @@ class RenderCommandEncoderImpl : public IRenderCommandEncoder, public CommandEnc
     setVertexBuffers(GfxIndex startSlot, GfxCount slotCount, IBuffer* const* buffers, const Offset* offsets) override;
 
     virtual SLANG_NO_THROW void SLANG_MCALL
-    setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset = 0) override;
+    setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset = 0) override;
 
     virtual SLANG_NO_THROW void SLANG_MCALL setStencilReference(uint32_t referenceValue) override;
 
diff --git a/src/vulkan/vk-command-encoder.cpp b/src/vulkan/vk-command-encoder.cpp
index 8d2bf2b4..237b35d3 100644
--- a/src/vulkan/vk-command-encoder.cpp
+++ b/src/vulkan/vk-command-encoder.cpp
@@ -1211,15 +1211,15 @@ void RenderCommandEncoderImpl::setVertexBuffers(
     }
 }
 
-void RenderCommandEncoderImpl::setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset)
+void RenderCommandEncoderImpl::setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset)
 {
     VkIndexType indexType = VK_INDEX_TYPE_UINT16;
     switch (indexFormat)
     {
-    case Format::R16_UINT:
+    case IndexFormat::UInt16:
         indexType = VK_INDEX_TYPE_UINT16;
         break;
-    case Format::R32_UINT:
+    case IndexFormat::UInt32:
         indexType = VK_INDEX_TYPE_UINT32;
         break;
     default:
diff --git a/src/vulkan/vk-command-encoder.h b/src/vulkan/vk-command-encoder.h
index c06784d5..6ad38e3d 100644
--- a/src/vulkan/vk-command-encoder.h
+++ b/src/vulkan/vk-command-encoder.h
@@ -206,7 +206,7 @@ class RenderCommandEncoderImpl : public IRenderCommandEncoder, public CommandEnc
     setVertexBuffers(GfxIndex startSlot, GfxCount slotCount, IBuffer* const* buffers, const Offset* offsets) override;
 
     virtual SLANG_NO_THROW void SLANG_MCALL
-    setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset = 0) override;
+    setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset = 0) override;
 
     Result prepareDraw();
 
diff --git a/src/wgpu/wgpu-command-encoder.cpp b/src/wgpu/wgpu-command-encoder.cpp
index ea0a9df6..aa26342e 100644
--- a/src/wgpu/wgpu-command-encoder.cpp
+++ b/src/wgpu/wgpu-command-encoder.cpp
@@ -436,13 +436,13 @@ void RenderCommandEncoderImpl::setVertexBuffers(
     }
 }
 
-void RenderCommandEncoderImpl::setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset)
+void RenderCommandEncoderImpl::setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset)
 {
     BufferImpl* bufferImpl = static_cast<BufferImpl*>(buffer);
     m_device->m_ctx.api.wgpuRenderPassEncoderSetIndexBuffer(
         m_renderPassEncoder,
         bufferImpl->m_buffer,
-        indexFormat == Format::R32_UINT ? WGPUIndexFormat_Uint32 : WGPUIndexFormat_Uint16,
+        indexFormat == IndexFormat::UInt32 ? WGPUIndexFormat_Uint32 : WGPUIndexFormat_Uint16,
         offset,
         bufferImpl->m_desc.size - offset
     );
diff --git a/src/wgpu/wgpu-command-encoder.h b/src/wgpu/wgpu-command-encoder.h
index e98c052a..532101a9 100644
--- a/src/wgpu/wgpu-command-encoder.h
+++ b/src/wgpu/wgpu-command-encoder.h
@@ -158,7 +158,7 @@ class RenderCommandEncoderImpl : public IRenderCommandEncoder, public CommandEnc
     setVertexBuffers(GfxIndex startSlot, GfxCount slotCount, IBuffer* const* buffers, const Offset* offsets) override;
 
     virtual SLANG_NO_THROW void SLANG_MCALL
-    setIndexBuffer(IBuffer* buffer, Format indexFormat, Offset offset = 0) override;
+    setIndexBuffer(IBuffer* buffer, IndexFormat indexFormat, Offset offset = 0) override;
 
     virtual SLANG_NO_THROW void SLANG_MCALL setStencilReference(uint32_t referenceValue) override;
 
diff --git a/tests/test-instanced-draw.cpp b/tests/test-instanced-draw.cpp
index 58721738..41672da0 100644
--- a/tests/test-instanced-draw.cpp
+++ b/tests/test-instanced-draw.cpp
@@ -301,7 +301,7 @@ struct DrawIndexedInstancedTest : BaseDrawTest
 
         encoder->setVertexBuffer(0, vertexBuffer);
         encoder->setVertexBuffer(1, instanceBuffer);
-        encoder->setIndexBuffer(indexBuffer, Format::R32_UINT);
+        encoder->setIndexBuffer(indexBuffer, IndexFormat::UInt32);
         encoder->setPrimitiveTopology(PrimitiveTopology::TriangleList);
 
         encoder->drawIndexedInstanced(kIndexCount, kInstanceCount, startIndex, startVertex, startInstanceLocation);
@@ -466,7 +466,7 @@ struct DrawIndexedIndirectTest : BaseDrawTest
 
         encoder->setVertexBuffer(0, vertexBuffer);
         encoder->setVertexBuffer(1, instanceBuffer);
-        encoder->setIndexBuffer(indexBuffer, Format::R32_UINT);
+        encoder->setIndexBuffer(indexBuffer, IndexFormat::UInt32);
         encoder->setPrimitiveTopology(PrimitiveTopology::TriangleList);
 
         uint32_t maxDrawCount = 1;