diff --git a/lib/Conversion/TorchOnnxToTorch/DefaultDomainAtoF.cpp b/lib/Conversion/TorchOnnxToTorch/DefaultDomainAtoF.cpp
index 3d2cf8aae..86f23bee1 100644
--- a/lib/Conversion/TorchOnnxToTorch/DefaultDomainAtoF.cpp
+++ b/lib/Conversion/TorchOnnxToTorch/DefaultDomainAtoF.cpp
@@ -836,6 +836,62 @@ void mlir::torch::onnx_c::populateDefaultDomainAtoF(
                       binder.op, resultType, operand);
                   return success();
                 });
+  patterns.onOp(
+      "CumSum", 11, [](OpBinder binder, ConversionPatternRewriter &rewriter) {
+        Location loc = binder.getLoc();
+        Torch::ValueTensorType resultType;
+        Value operand;
+        Value axisTensor;
+        if (binder.tensorOperands(operand, axisTensor) ||
+            binder.tensorResultType(resultType))
+          return failure();
+
+        int64_t exclusive;
+        int64_t reverse;
+        // if bind succeeds and either is set, fail because not implemented
+        if (binder.s64IntegerAttr(exclusive, "exclusive", 0))
+          if (exclusive != 0)
+            return rewriter.notifyMatchFailure(
+                binder.op, "unsupported onnx.CumSum conversion: exclusive");
+        if (binder.s64IntegerAttr(reverse, "reverse", 0))
+          if (reverse != 0)
+            return rewriter.notifyMatchFailure(
+                binder.op, "unsupported onnx.CumSum conversion: reverse");
+
+        // deal with neg axis: if (axis < 0) axis += rank
+        int64_t rank =
+            cast<Torch::ValueTensorType>(operand.getType()).getSizes().size();
+        Value rankVal = rewriter.create<Torch::ConstantIntOp>(
+            binder.getLoc(), rewriter.getType<Torch::IntType>(),
+            rewriter.getIntegerAttr(rewriter.getIntegerType(64),
+                                    rank));
+        Value zero = rewriter.create<Torch::ConstantIntOp>(
+            loc, rewriter.getI64IntegerAttr(0));
+        
+        Value axisScalar = rewriter.create<Torch::AtenItemOp>(
+            binder.getLoc(), rewriter.getType<Torch::IntType>(), axisTensor);
+        Value isNegative =
+            rewriter.create<Torch::AtenLtIntOp>(binder.getLoc(), axisScalar, zero);
+        isNegative = rewriter.create<Torch::AtenIntBoolOp>(binder.getLoc(),
+                                                            isNegative);
+        Value finalOffset = rewriter.create<Torch::AtenMulIntOp>(
+            binder.getLoc(), isNegative, rankVal);
+        Value dim = rewriter.create<Torch::AtenAddIntOp>(
+            binder.getLoc(), axisScalar, finalOffset);
+
+        Torch::BaseTensorType resultTensorType = resultType.cast<Torch::BaseTensorType>();
+        if (!resultTensorType.hasDtype()) {
+          return rewriter.notifyMatchFailure(
+              binder.op, "expected result type to have a dtype");
+        }
+        // resultTensorType.print(llvm::outs());
+        Value resultDType =
+            Torch::getDtypeIntValueForType(rewriter, loc, resultTensorType.getDtype());
+
+        rewriter.replaceOpWithNewOp<Torch::AtenCumsumOp>(
+            binder.op, resultType, operand, dim, resultDType);
+        return success();
+      });
   patterns.onOp("Div", 14,
                 [](OpBinder binder, ConversionPatternRewriter &rewriter) {
                   Torch::ValueTensorType resultType;
diff --git a/test/Conversion/TorchOnnxToTorch/unsupported_fb_opt_ops.mlir b/test/Conversion/TorchOnnxToTorch/unsupported_fb_opt_ops.mlir
index 3ed9f1c6e..6659935ff 100644
--- a/test/Conversion/TorchOnnxToTorch/unsupported_fb_opt_ops.mlir
+++ b/test/Conversion/TorchOnnxToTorch/unsupported_fb_opt_ops.mlir
@@ -36,4 +36,13 @@ func.func @reduce_mean_operation(%arg0: !torch.vtensor<[1,64,768],f32>)
   // The ReduceMean operation as provided.
   %211 = torch.operator "onnx.ReduceMean"(%arg0) {torch.onnx.axes = [-1 : si64]} : (!torch.vtensor<[1,64,768],f32>) -> !torch.vtensor<[1,64,1],f32>
   return %211 : !torch.vtensor<[1,64,1],f32>
+}
+
+// -----
+// Fixed.
+func.func @cumsum_operation(%arg0: !torch.vtensor<[2,3],f64>, 
+                            %arg1: !torch.vtensor<[],si32>) 
+                            -> !torch.vtensor<[2,3],f64> attributes {torch.onnx_meta.ir_version = 9 : si64, torch.onnx_meta.opset_version = 11 : si64, torch.onnx_meta.producer_name = "backend-test", torch.onnx_meta.producer_version = ""} {
+  %212 = torch.operator "onnx.CumSum"(%arg0, %arg1) : (!torch.vtensor<[2,3],f64>, !torch.vtensor<[],si32>) -> !torch.vtensor<[2,3],f64>
+  return %212 : !torch.vtensor<[2,3],f64>
 }
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