diff --git a/app/src/BooksUtil.cpp b/app/src/BooksUtil.cpp
index 70e21b9..d4e7dc6 100644
--- a/app/src/BooksUtil.cpp
+++ b/app/src/BooksUtil.cpp
@@ -90,7 +90,7 @@ shared_ptr<Book> BooksUtil::bookFromFile(std::string aPath)
     return book;
 }
 
-QByteArray BooksUtil::computeFileHash(QString aPath, BooksTask* aTask)
+QByteArray BooksUtil::computeFileHash(QString aPath, const BooksTask* aTask)
 {
     QByteArray result;
     QFile file(aPath);
@@ -157,7 +157,7 @@ bool BooksUtil::setFileHashAttr(QString aPath, QByteArray aHash)
     return false;
 }
 
-QByteArray BooksUtil::computeFileHashAndSetAttr(QString aPath, BooksTask* aTask)
+QByteArray BooksUtil::computeFileHashAndSetAttr(QString aPath, const BooksTask* aTask)
 {
     QByteArray hash = computeFileHash(aPath, aTask);
     if (!hash.isEmpty()) {
diff --git a/app/src/BooksUtil.h b/app/src/BooksUtil.h
index 506e844..4bec122 100644
--- a/app/src/BooksUtil.h
+++ b/app/src/BooksUtil.h
@@ -48,8 +48,8 @@ namespace BooksUtil {
     bool isValidFileName(QString aName);
     QByteArray fileHashAttr(QString aPath);
     bool setFileHashAttr(QString aPath, QByteArray aHash);
-    QByteArray computeFileHash(QString aPath, BooksTask* aTask = NULL);
-    QByteArray computeFileHashAndSetAttr(QString aPath, BooksTask* aTask = NULL);
+    QByteArray computeFileHash(QString aPath, const BooksTask* aTask = NULL);
+    QByteArray computeFileHashAndSetAttr(QString aPath, const BooksTask* aTask = NULL);
 }
 
 inline shared_ptr<Book> BooksUtil::bookFromFile(QString aPath)