diff --git a/src/book.cpp b/src/book.cpp
index 6a173ba9c..6d41a87eb 100644
--- a/src/book.cpp
+++ b/src/book.cpp
@@ -87,7 +87,7 @@ void Book::update(const kiwix::Reader& reader)
   m_origId = reader.getOrigId();
   m_articleCount = reader.getArticleCount();
   m_mediaCount = reader.getMediaCount();
-  m_size = reader.getFileSize() << 10;
+  m_size = static_cast<uint64_t>(reader.getFileSize()) << 10;
 
   reader.getFavicon(m_favicon, m_faviconMimeType);
 }
diff --git a/src/library.cpp b/src/library.cpp
index ef1a65d1a..34650c2f8 100644
--- a/src/library.cpp
+++ b/src/library.cpp
@@ -145,10 +145,10 @@ bool Library::writeToFile(const std::string& path) {
         bookNode.append_attribute("url") = book.getUrl().c_str();
       }
 
-      if (!book.getArticleCount())
+      if (book.getArticleCount())
         bookNode.append_attribute("articleCount") = to_string(book.getArticleCount()).c_str();
 
-      if (!book.getMediaCount())
+      if (book.getMediaCount())
         bookNode.append_attribute("mediaCount") = to_string(book.getMediaCount()).c_str();
 
       if (book.getSize()) {
diff --git a/src/reader.cpp b/src/reader.cpp
index 00ac9a48e..abe704de6 100644
--- a/src/reader.cpp
+++ b/src/reader.cpp
@@ -851,7 +851,7 @@ bool Reader::isCorrupted() const
 unsigned int Reader::getFileSize() const
 {
   zim::File* file = this->getZimFileHandler();
-  zim::offset_type size = 0;
+  zim::size_type size = 0;
 
   if (file != NULL) {
     size = file->getFilesize();