diff --git a/velox/common/file/File.h b/velox/common/file/File.h
index 32f8540eb3acc..53128c3dbe834 100644
--- a/velox/common/file/File.h
+++ b/velox/common/file/File.h
@@ -251,7 +251,7 @@ struct HeapMemoryMock {
     size_ += len;
   }
 
-  void read(void* dst, size_ len, size_t offset) {
+  void read(void* dst, size_t len, size_t offset) {
     assert(offset + len <= size_);
     memcpy(dst, (char*)memory_ + offset, len);
   }
diff --git a/velox/exec/Spill.cpp b/velox/exec/Spill.cpp
index 926cac340cf3c..76cb1af58bf12 100644
--- a/velox/exec/Spill.cpp
+++ b/velox/exec/Spill.cpp
@@ -77,12 +77,13 @@ void SpillFile::startRead() {
     auto buffer = AlignedBuffer::allocate<char>(
         std::min<uint64_t>(fileSize_, kMaxReadBufferSize), &pool_);
     input_ = std::make_unique<SpillInput>(std::move(file), std::move(buffer));
-  } else {
-    std::unique_ptr<ReadFile> =
-        std::make_unique<HeapMemoryReadFile>(heapMemoryMock_);
+  } else if (toWhere_ == TO_HEAP) {
+    auto file = std::make_unique<HeapMemoryReadFile>(heapMemoryMock_);
     auto buffer = AlignedBuffer::allocate<char>(
         std::min<uint64_t>(fileSize_, kMaxReadBufferSize), &pool_);
     input_ = std::make_unique<SpillInput>(std::move(file), std::move(buffer));
+  } else {
+    VELOX_FAIL("invalid spill destination");
   }
 }