diff --git a/lang/c++/impl/DataFile.cc b/lang/c++/impl/DataFile.cc
index 5bf27c1ab7c..c9b9c8420e9 100644
--- a/lang/c++/impl/DataFile.cc
+++ b/lang/c++/impl/DataFile.cc
@@ -489,7 +489,7 @@ void DataFileReaderBase::readDataBlock() {
         }
 
         // Get the decompressed size
-        size_t decompressed_size = ZSTD_getFrameContentSize(
+        unsigned long long decompressed_size = ZSTD_getFrameContentSize(
             reinterpret_cast<const char *>(compressed_.data()), compressed_.size());
         if (decompressed_size == ZSTD_CONTENTSIZE_ERROR) {
             throw Exception("ZSTD: Not a valid compressed frame");