diff --git a/Common/onelab.h b/Common/onelab.h
index 051aecfa017cd3217c874ad69c1527b22f286937..4f35d1bf12f7234b2a9d5deb9dc5138374d30e82 100644
--- a/Common/onelab.h
+++ b/Common/onelab.h
@@ -595,8 +595,8 @@ namespace onelab{
     void setPid(int pid){ _pid = pid; }
     GmshServer *getGmshServer(){ return _gmshServer; }
     void setGmshServer(GmshServer *server){ _gmshServer = server; }
-    virtual bool run(const std::string &what){ return false; }
-    virtual bool kill(){ return false; }
+    virtual bool run(const std::string &what);
+    virtual bool kill();
   };
 
   class remoteNetworkClient : public client{
diff --git a/Fltk/onelabWindow.cpp b/Fltk/onelabWindow.cpp
index f074a14ed1f4e94c28dcd0ef83846c776b28ae3e..baf63b965d4fbb40e75f36a76c1105d36b234aba 100644
--- a/Fltk/onelabWindow.cpp
+++ b/Fltk/onelabWindow.cpp
@@ -5,6 +5,7 @@
 
 #include <FL/Fl.H>
 #include "GmshMessage.h"
+#include "onelab.h"
 #if (FL_MAJOR_VERSION == 1) && (FL_MINOR_VERSION == 3)
 #include <FL/Fl_Value_Input.H>
 #include <FL/Fl_Input_Choice.H>
@@ -641,6 +642,16 @@ void solver_cb(Fl_Widget *w, void *data)
 
 #else
 
+bool onelab::localNetworkClient::run(const std::string &what)
+{
+  Msg::Error("The solver interface requires FLTK 1.3");
+}
+
+bool onelab::localNetworkClient::kill()
+{
+  Msg::Error("The solver interface requires FLTK 1.3");
+}
+
 void solver_cb(Fl_Widget *w, void *data)
 {
   Msg::Error("The solver interface requires FLTK 1.3");