diff --git a/ethosu/regor/architecture/ethosu55/ethos_u55_constraints.cpp b/ethosu/regor/architecture/ethosu55/ethos_u55_constraints.cpp
index 021959a240cc168044e107936ece0a8f9ca23f04..da197be95af2ec642e1eaa0b5f10f9c2004792a5 100644
--- a/ethosu/regor/architecture/ethosu55/ethos_u55_constraints.cpp
+++ b/ethosu/regor/architecture/ethosu55/ethos_u55_constraints.cpp
@@ -114,7 +114,7 @@ bool EthosU55Constraints::SupportsFusedRescale(OpType opType, TensorUsage tensor
         }
         else if ( npuOp == EthosU55NpuOp::ReduceSum )
         {
-            return globalScale;
+            return globalScale && isUnitScale;
         }
     }
     else if ( tensorUsage == TensorUsage::OFM )
diff --git a/ethosu/regor/architecture/ethosu85/ethos_u85_constraints.cpp b/ethosu/regor/architecture/ethosu85/ethos_u85_constraints.cpp
index 6ab78def8fd8486ba44614ff28d4271f29c5528f..7988eb91e1b40761cc795f565f5e02de258e97f7 100644
--- a/ethosu/regor/architecture/ethosu85/ethos_u85_constraints.cpp
+++ b/ethosu/regor/architecture/ethosu85/ethos_u85_constraints.cpp
@@ -132,7 +132,7 @@ bool EthosU85Constraints::SupportsFusedRescale(OpType opType, TensorUsage tensor
         }
         else if ( npuOp == EthosU85NpuOp::ReduceSum )
         {
-            return globalScale;
+            return globalScale && isUnitScale;
         }
     }
     else if ( tensorUsage == TensorUsage::OFM )