diff --git a/compiler/lib/Conversion/FHEToTFHECrt/FHEToTFHECrt.cpp b/compiler/lib/Conversion/FHEToTFHECrt/FHEToTFHECrt.cpp
index 8fc778e07..e038dfee3 100644
--- a/compiler/lib/Conversion/FHEToTFHECrt/FHEToTFHECrt.cpp
+++ b/compiler/lib/Conversion/FHEToTFHECrt/FHEToTFHECrt.cpp
@@ -741,6 +741,82 @@ struct TensorReassociationOpPattern : public CrtOpPattern<Op> {
   };
 };
 
+struct ExtractSliceOpPattern
+    : public CrtOpPattern<mlir::tensor::ExtractSliceOp> {
+  ExtractSliceOpPattern(mlir::MLIRContext *context,
+                        concretelang::CrtLoweringParameters params,
+                        mlir::PatternBenefit benefit = 1)
+      : CrtOpPattern<mlir::tensor::ExtractSliceOp>(context, params, benefit) {}
+
+  ::mlir::LogicalResult
+  matchAndRewrite(mlir::tensor::ExtractSliceOp op,
+                  mlir::tensor::ExtractSliceOp::Adaptor adaptor,
+                  ::mlir::ConversionPatternRewriter &rewriter) const override {
+
+    mlir::TypeConverter *converter = this->getTypeConverter();
+
+    mlir::SmallVector<mlir::Attribute> newStaticOffsets{
+        op.static_offsets().template getAsRange<mlir::IntegerAttr>()};
+    mlir::SmallVector<mlir::Attribute> newStaticSizes{
+        op.static_sizes().template getAsRange<mlir::IntegerAttr>()};
+    mlir::SmallVector<mlir::Attribute> newStaticStrides{
+        op.static_strides().template getAsRange<mlir::IntegerAttr>()};
+    newStaticOffsets.push_back(rewriter.getI64IntegerAttr(0));
+    newStaticSizes.push_back(
+        rewriter.getI64IntegerAttr(this->loweringParameters.nMods));
+    newStaticStrides.push_back(rewriter.getI64IntegerAttr(1));
+
+    mlir::RankedTensorType newType =
+        converter->convertType(op.getResult().getType())
+            .template cast<mlir::RankedTensorType>();
+    rewriter.replaceOpWithNewOp<mlir::tensor::ExtractSliceOp>(
+        op, newType, adaptor.source(), adaptor.getOffsets(), adaptor.getSizes(),
+        adaptor.getStrides(), rewriter.getArrayAttr(newStaticOffsets),
+        rewriter.getArrayAttr(newStaticSizes),
+        rewriter.getArrayAttr(newStaticStrides));
+
+    return mlir::success();
+  };
+};
+
+struct InsertSliceOpPattern : public CrtOpPattern<mlir::tensor::InsertSliceOp> {
+  InsertSliceOpPattern(mlir::MLIRContext *context,
+                       concretelang::CrtLoweringParameters params,
+                       mlir::PatternBenefit benefit = 1)
+      : CrtOpPattern<mlir::tensor::InsertSliceOp>(context, params, benefit) {}
+
+  ::mlir::LogicalResult
+  matchAndRewrite(mlir::tensor::InsertSliceOp op,
+                  mlir::tensor::InsertSliceOp::Adaptor adaptor,
+                  ::mlir::ConversionPatternRewriter &rewriter) const override {
+
+    mlir::TypeConverter *converter = this->getTypeConverter();
+
+    mlir::SmallVector<mlir::Attribute> newStaticOffsets{
+        op.static_offsets().template getAsRange<mlir::IntegerAttr>()};
+    mlir::SmallVector<mlir::Attribute> newStaticSizes{
+        op.static_sizes().template getAsRange<mlir::IntegerAttr>()};
+    mlir::SmallVector<mlir::Attribute> newStaticStrides{
+        op.static_strides().template getAsRange<mlir::IntegerAttr>()};
+    newStaticOffsets.push_back(rewriter.getI64IntegerAttr(0));
+    newStaticSizes.push_back(
+        rewriter.getI64IntegerAttr(this->loweringParameters.nMods));
+    newStaticStrides.push_back(rewriter.getI64IntegerAttr(1));
+
+    mlir::RankedTensorType newType =
+        converter->convertType(op.getResult().getType())
+            .template cast<mlir::RankedTensorType>();
+    rewriter.replaceOpWithNewOp<mlir::tensor::InsertSliceOp>(
+        op, newType, adaptor.source(), adaptor.dest(), adaptor.getOffsets(),
+        adaptor.getSizes(), adaptor.getStrides(),
+        rewriter.getArrayAttr(newStaticOffsets),
+        rewriter.getArrayAttr(newStaticSizes),
+        rewriter.getArrayAttr(newStaticStrides));
+
+    return mlir::success();
+  };
+};
+
 } // namespace lowering
 
 struct FHEToTFHECrtPass : public FHEToTFHECrtBase<FHEToTFHECrtPass> {
@@ -865,16 +941,16 @@ struct FHEToTFHECrtPass : public FHEToTFHECrtBase<FHEToTFHECrtPass> {
                                                    loweringParameters);
     patterns.add<lowering::TensorInsertOpPattern>(&getContext(),
                                                   loweringParameters);
-    patterns.add<concretelang::TypeConvertingReinstantiationPattern<
-        mlir::tensor::ExtractSliceOp>>(patterns.getContext(), converter);
-    patterns.add<concretelang::TypeConvertingReinstantiationPattern<
-        mlir::tensor::InsertSliceOp>>(patterns.getContext(), converter);
     patterns.add<lowering::TensorReassociationOpPattern<
         mlir::tensor::CollapseShapeOp, true>>(patterns.getContext(),
                                               loweringParameters);
     patterns.add<lowering::TensorReassociationOpPattern<
         mlir::tensor::ExpandShapeOp, false>>(patterns.getContext(),
                                              loweringParameters);
+    patterns.add<lowering::ExtractSliceOpPattern>(patterns.getContext(),
+                                                  loweringParameters);
+    patterns.add<lowering::InsertSliceOpPattern>(patterns.getContext(),
+                                                 loweringParameters);
     patterns.add<concretelang::TypeConvertingReinstantiationPattern<
         mlir::tensor::GenerateOp, true>>(&getContext(), converter);
 
diff --git a/compiler/tests/check_tests/BugReport/bug_report_858.mlir b/compiler/tests/check_tests/BugReport/bug_report_858.mlir
new file mode 100644
index 000000000..b75f3da50
--- /dev/null
+++ b/compiler/tests/check_tests/BugReport/bug_report_858.mlir
@@ -0,0 +1,10 @@
+// RUN: concretecompiler --action=dump-tfhe --force-encoding crt %s
+func.func @main(%arg0: tensor<32x!FHE.eint<8>>) -> tensor<16x!FHE.eint<8>>{
+ %0 = tensor.extract_slice %arg0[16] [16] [1] : tensor<32x!FHE.eint<8>> to tensor<16x!FHE.eint<8>>
+ return %0 : tensor<16x!FHE.eint<8>>
+}
+
+func.func @main2(%t0: tensor<2x10x!FHE.eint<6>>, %t1: tensor<2x2x!FHE.eint<6>>) -> tensor<2x10x!FHE.eint<6>> {
+  %r = tensor.insert_slice %t1 into %t0[0, 5][2, 2][1, 1] : tensor<2x2x!FHE.eint<6>> into tensor<2x10x!FHE.eint<6>>
+  return %r : tensor<2x10x!FHE.eint<6>>
+}