diff --git a/compiler/lib/Conversion/ConcreteToBConcrete/ConcreteToBConcrete.cpp b/compiler/lib/Conversion/ConcreteToBConcrete/ConcreteToBConcrete.cpp
index 45a28ad37..8f31d339d 100644
--- a/compiler/lib/Conversion/ConcreteToBConcrete/ConcreteToBConcrete.cpp
+++ b/compiler/lib/Conversion/ConcreteToBConcrete/ConcreteToBConcrete.cpp
@@ -208,12 +208,10 @@ struct LowerKeySwitch : public mlir::OpRewritePattern<
     // construct attributes for in/out dimensions
     mlir::concretelang::Concrete::LweCiphertextType outType = ksOp.getType();
     auto outDimAttr = rewriter.getI32IntegerAttr(outType.getDimension());
-    auto inputType =
-        ksOp.ciphertext()
-            .getType()
-            .cast<mlir::concretelang::Concrete::LweCiphertextType>();
-    mlir::IntegerAttr inputDimAttr =
-        rewriter.getI32IntegerAttr(inputType.getDimension());
+    auto inputType = converter.convertType(ksOp.ciphertext().getType())
+                         .cast<mlir::RankedTensorType>();
+    auto inputDimension = inputType.getShape().back() - 1;
+    mlir::IntegerAttr inputDimAttr = rewriter.getI32IntegerAttr(inputDimension);
 
     mlir::Operation *bKeySwitchOp = rewriter.replaceOpWithNewOp<
         mlir::concretelang::BConcrete::KeySwitchLweTensorOp>(
@@ -286,11 +284,11 @@ struct LowerBootstrap : public mlir::OpRewritePattern<
     ConcreteToBConcreteTypeConverter converter;
 
     mlir::concretelang::Concrete::LweCiphertextType outType = bsOp.getType();
-    auto inputType =
-        bsOp.input_ciphertext()
-            .getType()
-            .cast<mlir::concretelang::Concrete::LweCiphertextType>();
-    auto inputDimAttr = rewriter.getI32IntegerAttr(inputType.getDimension());
+    auto inputType = converter.convertType(bsOp.input_ciphertext().getType())
+                         .cast<mlir::RankedTensorType>();
+    auto inputDimension = inputType.getShape().back() - 1;
+    mlir::IntegerAttr inputDimAttr = rewriter.getI32IntegerAttr(inputDimension);
+
     auto outputPrecisionAttr = rewriter.getI32IntegerAttr(outType.getP());
     mlir::Operation *bBootstrapOp = rewriter.replaceOpWithNewOp<
         mlir::concretelang::BConcrete::BootstrapLweTensorOp>(
diff --git a/compiler/tests/end_to_end_fixture/end_to_end_fhe.yaml b/compiler/tests/end_to_end_fixture/end_to_end_fhe.yaml
index 75773f8bf..796d8ac6e 100644
--- a/compiler/tests/end_to_end_fixture/end_to_end_fhe.yaml
+++ b/compiler/tests/end_to_end_fixture/end_to_end_fhe.yaml
@@ -289,3 +289,32 @@ tests:
     - scalar: 63
     outputs:
     - scalar: 12
+---
+# https://github.com/zama-ai/concrete-compiler-internal/issues/809
+description: bug_809
+program: |
+  func.func @main(%arg0: !FHE.eint<6>) -> !FHE.eint<6> {
+    %cst = arith.constant dense<[1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1]> : tensor<64xi64>
+    %0 = "FHE.apply_lookup_table"(%arg0, %cst) : (!FHE.eint<6>, tensor<64xi64>) -> !FHE.eint<6>
+    %cst_0 = arith.constant dense<[0, 10, 20, 30, 40, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73]> : tensor<64xi64>
+    %1 = "FHE.apply_lookup_table"(%arg0, %cst_0) : (!FHE.eint<6>, tensor<64xi64>) -> !FHE.eint<6>
+    %2 = "FHE.add_eint"(%0, %1) : (!FHE.eint<6>, !FHE.eint<6>) -> !FHE.eint<6>
+    return %2 : !FHE.eint<6>
+  }
+tests:
+  - inputs:
+    - scalar: 0
+    outputs:
+    - scalar: 1
+  - inputs:
+    - scalar: 5
+    outputs:
+    - scalar: 15
+  - inputs:
+    - scalar: 62
+    outputs:
+    - scalar: 72
+  - inputs:
+    - scalar: 63
+    outputs:
+    - scalar: 74