diff --git a/src/plugins/scripts/python/weechat-python.c b/src/plugins/scripts/python/weechat-python.c
index 4e50072a7..8f024fde4 100644
--- a/src/plugins/scripts/python/weechat-python.c
+++ b/src/plugins/scripts/python/weechat-python.c
@@ -91,14 +91,20 @@ weechat_python_exec (t_weechat_plugin *plugin,
     else
         rc = PyObject_CallFunction (evFunc, "");
 
+    
+    if (rc == Py_None)
+    {
+	python_plugin->print_server (python_plugin, "Python error: function \"%s\" must return a valid value", function);
+	return PLUGIN_RC_OK;
+    }
+
     if (rc)
     {
         ret = (int) PyInt_AsLong(rc);
         Py_XDECREF(rc);
     }
     
-    if (PyErr_Occurred ())
-	PyErr_Print ();
+    if (PyErr_Occurred ()) PyErr_Print ();
     
     if (ret < 0)
         return PLUGIN_RC_OK;
diff --git a/src/plugins/scripts/ruby/weechat-ruby.c b/src/plugins/scripts/ruby/weechat-ruby.c
index 8a35cbf5a..6e0767f6b 100644
--- a/src/plugins/scripts/ruby/weechat-ruby.c
+++ b/src/plugins/scripts/ruby/weechat-ruby.c
@@ -153,6 +153,12 @@ weechat_ruby_exec (t_weechat_plugin *plugin,
 	
         return PLUGIN_RC_KO;
     }
+
+    if (ruby_retcode == Qnil)
+    {
+	ruby_plugin->print_server (ruby_plugin, "Ruby error: function \"%s\" must return a valid value", function);
+	return PLUGIN_RC_OK;
+    }
     
     return NUM2INT(ruby_retcode);
 }
diff --git a/weechat/src/plugins/scripts/python/weechat-python.c b/weechat/src/plugins/scripts/python/weechat-python.c
index 4e50072a7..8f024fde4 100644
--- a/weechat/src/plugins/scripts/python/weechat-python.c
+++ b/weechat/src/plugins/scripts/python/weechat-python.c
@@ -91,14 +91,20 @@ weechat_python_exec (t_weechat_plugin *plugin,
     else
         rc = PyObject_CallFunction (evFunc, "");
 
+    
+    if (rc == Py_None)
+    {
+	python_plugin->print_server (python_plugin, "Python error: function \"%s\" must return a valid value", function);
+	return PLUGIN_RC_OK;
+    }
+
     if (rc)
     {
         ret = (int) PyInt_AsLong(rc);
         Py_XDECREF(rc);
     }
     
-    if (PyErr_Occurred ())
-	PyErr_Print ();
+    if (PyErr_Occurred ()) PyErr_Print ();
     
     if (ret < 0)
         return PLUGIN_RC_OK;
diff --git a/weechat/src/plugins/scripts/ruby/weechat-ruby.c b/weechat/src/plugins/scripts/ruby/weechat-ruby.c
index 8a35cbf5a..6e0767f6b 100644
--- a/weechat/src/plugins/scripts/ruby/weechat-ruby.c
+++ b/weechat/src/plugins/scripts/ruby/weechat-ruby.c
@@ -153,6 +153,12 @@ weechat_ruby_exec (t_weechat_plugin *plugin,
 	
         return PLUGIN_RC_KO;
     }
+
+    if (ruby_retcode == Qnil)
+    {
+	ruby_plugin->print_server (ruby_plugin, "Ruby error: function \"%s\" must return a valid value", function);
+	return PLUGIN_RC_OK;
+    }
     
     return NUM2INT(ruby_retcode);
 }