diff --git a/device/UT/UTDecoding/src/UTClusterAndPreDecode.cu b/device/UT/UTDecoding/src/UTClusterAndPreDecode.cu
index 169e033b1b51ee1a76a2af001a3d28411cf29d71..64dd0b7459f8a0d9de0f3d6b45579c696adcecbf 100644
--- a/device/UT/UTDecoding/src/UTClusterAndPreDecode.cu
+++ b/device/UT/UTDecoding/src/UTClusterAndPreDecode.cu
@@ -152,7 +152,7 @@ __device__ void store_predecoded_ut_cluster(
   UT::PreDecodedHits ut_pre_decoded_hits)
 {
   // we need to know whether or not a "stripflip" canges the numbering
-  const auto numstrips = p0Z < 0 ? UT::Decoding::v5::strips_per_hybrid - mean_strip : mean_strip;
+  const auto numstrips = p0Z < 0 ? UT::Decoding::v5::strips_per_hybrid - 1 - mean_strip : mean_strip;
 
   const uint32_t LHCbID = lhcb_id::set_detector_type_id(lhcb_id::LHCbIDType::UT, (fullSectorID + stripID));