diff --git a/algo/detectors/sts/ReadoutConfig.cxx b/algo/detectors/sts/ReadoutConfig.cxx
index 14fd5c59b075c1faf86fb68b2ae5fb24d4057d28..ee8e7b824d656d9a3637f0e65dd0554fb93b5b21 100644
--- a/algo/detectors/sts/ReadoutConfig.cxx
+++ b/algo/detectors/sts/ReadoutConfig.cxx
@@ -135,7 +135,7 @@ void sts::ReadoutConfig::Init(const ReadoutSetup& config, const ChannelMaskSet&
 
         // Init channel mask
         const int32_t numFebsPerCrob = component.FEBsPerCrob();
-        const int32_t febId          = feb + compIdx * numCrobPerComp * numFebsPerCrob;
+        const int32_t febId          = 2 * moduleIdx + moduleSide;
         auto mapIt                   = chanMaskSet.values.find(febId);
         if (mapIt != chanMaskSet.values.end()) {
           const auto& mask = mapIt->second;