diff --git a/rtgui/toolpanel.cc b/rtgui/toolpanel.cc
index 6db30bb14..46899f1a2 100644
--- a/rtgui/toolpanel.cc
+++ b/rtgui/toolpanel.cc
@@ -47,6 +47,11 @@ ToolParamBlock::ToolParamBlock() {
 //GTK318
 }
 
+Gtk::SizeRequestMode ToolParamBlock::get_request_mode_vfunc () const
+{
+    return Gtk::SIZE_REQUEST_HEIGHT_FOR_WIDTH;
+}
+
 FoldableToolPanel::FoldableToolPanel(Gtk::Box* content, Glib::ustring toolName, Glib::ustring UILabel, bool need11, bool useEnabled) : ToolPanel(toolName, need11), parentContainer(nullptr), exp(nullptr), lastEnabled(true)
 {
     if (!content) {
diff --git a/rtgui/toolpanel.h b/rtgui/toolpanel.h
index 5ec59c9c2..f22f6f771 100644
--- a/rtgui/toolpanel.h
+++ b/rtgui/toolpanel.h
@@ -70,6 +70,7 @@ class ToolParamBlock :
 {
 public:
     ToolParamBlock();
+    Gtk::SizeRequestMode get_request_mode_vfunc () const override;
 };
 
 class ToolPanel :