diff --git a/rtgui/darkframe.h b/rtgui/darkframe.h
index 85f614260..92f475100 100755
--- a/rtgui/darkframe.h
+++ b/rtgui/darkframe.h
@@ -28,7 +28,7 @@
 class DFProvider {
   public:
     virtual rtengine::RawImage* getDF() = 0;
-    virtual Glib::ustring GetCurrentImageFilePath() {};
+    virtual Glib::ustring GetCurrentImageFilePath() = 0;
     // add other info here
 };
 
diff --git a/rtgui/flatfield.h b/rtgui/flatfield.h
index c03afaca5..12f9dacba 100755
--- a/rtgui/flatfield.h
+++ b/rtgui/flatfield.h
@@ -30,7 +30,7 @@ class FFProvider {
   public:
     virtual ~FFProvider() {}
     virtual rtengine::RawImage* getFF() = 0;
-    virtual Glib::ustring GetCurrentImageFilePath() {};
+    virtual Glib::ustring GetCurrentImageFilePath() = 0;
     // add other info here
 };