diff --git a/gemma/weights.cc b/gemma/weights.cc
index 4c1f482..d8f1491 100644
--- a/gemma/weights.cc
+++ b/gemma/weights.cc
@@ -367,7 +367,7 @@ static void MapAll(const std::vector<TensorToRead>& tensors,
 // Mode == kReadBF16:
 
 template <typename T>
-static void DecompressToBF16(const MatPtr& mat,
+static void DecompressToBF16(MatPtr& mat,
                              const hwy::AlignedFreeUniquePtr<uint8_t[]>& buf) {
   hwy::HWY_NAMESPACE::ScalableTag<BF16> dbf;
   const size_t cols = mat.Cols();