diff --git a/rtgui/dirbrowser.cc b/rtgui/dirbrowser.cc
index 9ed8455fe..81ee85fed 100644
--- a/rtgui/dirbrowser.cc
+++ b/rtgui/dirbrowser.cc
@@ -220,7 +220,7 @@ void DirBrowser::updateDirTree (const Gtk::TreeModel::iterator& iter)
 void DirBrowser::updateVolumes ()
 {
 
-    int nvolumes = GetLogicalDrives ();
+    unsigned int nvolumes = GetLogicalDrives ();
 
     if (nvolumes != volumes) {
         GThreadLock lock;
diff --git a/rtgui/dirbrowser.h b/rtgui/dirbrowser.h
index e8eefdd36..a3f451101 100644
--- a/rtgui/dirbrowser.h
+++ b/rtgui/dirbrowser.h
@@ -84,7 +84,7 @@ private:
     bool expandSuccess;
 
 #ifdef WIN32
-    int volumes;
+    unsigned int volumes;
 public:
     void updateVolumes ();
     void updateDirTree  (const Gtk::TreeModel::iterator& iter);