diff --git a/core/fileprinter.cpp b/core/fileprinter.cpp
index 52334da1a..149a36bbb 100644
--- a/core/fileprinter.cpp
+++ b/core/fileprinter.cpp
@@ -31,7 +31,7 @@
 
 using namespace Okular;
 
-int FilePrinter::printFile( QPrinter &printer, QString file, FileDeletePolicy fileDeletePolicy,
+int FilePrinter::printFile( QPrinter &printer, const QString &file, FileDeletePolicy fileDeletePolicy,
                             PageSelectPolicy pageSelectPolicy, const QString &pageRange )
 {
     FilePrinter fp;
@@ -44,7 +44,7 @@ int FilePrinter::printFiles( QPrinter &printer, const QStringList &fileList, Fil
     return fp.doPrintFiles( printer, fileList, fileDeletePolicy, FilePrinter::ApplicationSelectsPages, QString() );
 }
 
-int FilePrinter::doPrintFiles( QPrinter &printer, QStringList fileList, FileDeletePolicy fileDeletePolicy,
+int FilePrinter::doPrintFiles( QPrinter &printer, const QStringList &fileList, FileDeletePolicy fileDeletePolicy,
                                PageSelectPolicy pageSelectPolicy, const QString &pageRange )
 {
     QString exe("lpr");
diff --git a/core/fileprinter.h b/core/fileprinter.h
index b7ab1f2b7..1aa8be0c9 100644
--- a/core/fileprinter.h
+++ b/core/fileprinter.h
@@ -68,7 +68,7 @@ public:
      *          otherwise the KProcess exit code
      */
 
-    static int printFile( QPrinter &printer, const QString file,
+    static int printFile( QPrinter &printer, const QString &file,
                           FileDeletePolicy fileDeletePolicy = FilePrinter::ApplicationDeletesFiles,
                           PageSelectPolicy pageSelectPolicy = FilePrinter::ApplicationSelectsPages,
                           const QString &pageRange = QString() );
@@ -137,7 +137,7 @@ protected:
     bool detectCupsService();
     bool detectCupsConfig();
 
-    int doPrintFiles( QPrinter &printer, const QStringList fileList,
+    int doPrintFiles( QPrinter &printer, const QStringList &fileList,
                              FileDeletePolicy fileDeletePolicy, PageSelectPolicy pageSelectPolicy,
                              const QString &pageRange );