diff --git a/source/common/buffer/buffer_impl.cc b/source/common/buffer/buffer_impl.cc
index b57173a1f3b8b..3d2b274834664 100644
--- a/source/common/buffer/buffer_impl.cc
+++ b/source/common/buffer/buffer_impl.cc
@@ -206,7 +206,8 @@ RawSlice OwnedImpl::frontSlice() const {
   // Ignore zero-size slices and return the first slice with data.
   for (const auto& slice : slices_) {
     if (slice.dataSize() > 0) {
-      return RawSlice{const_cast<uint8_t*>(slice.data()), slice.dataSize()};
+      return RawSlice{const_cast<uint8_t*>(slice.data()),
+                      static_cast<absl::Span<uint8_t>::size_type>(slice.dataSize())};
     }
   }
 
diff --git a/source/common/buffer/buffer_impl.h b/source/common/buffer/buffer_impl.h
index eaecb5d719ff2..c557107df0505 100644
--- a/source/common/buffer/buffer_impl.h
+++ b/source/common/buffer/buffer_impl.h
@@ -326,7 +326,7 @@ class SliceDataImpl : public SliceData {
   // SliceData
   absl::Span<uint8_t> getMutableData() override {
     RELEASE_ASSERT(slice_.isMutable(), "Not allowed to call getMutableData if slice is immutable");
-    return {slice_.data(), slice_.dataSize()};
+    return {slice_.data(), static_cast<absl::Span<uint8_t>::size_type>(slice_.dataSize())};
   }
 
 private: