diff --git a/include/wx/gtk/toplevel.h b/include/wx/gtk/toplevel.h
index 2cf22d8e41..ac2e27a7fd 100644
--- a/include/wx/gtk/toplevel.h
+++ b/include/wx/gtk/toplevel.h
@@ -138,6 +138,16 @@ public:
 
     void GTKDoAfterShow();
 
+#ifdef __WXGTK3__
+    void GTKUpdateClientSizeIfNecessary();
+
+    virtual void WXSetInitialFittingClientSize(int flags) wxOVERRIDE;
+
+private:
+    // Flags to call WXSetInitialFittingClientSize() with if != 0.
+    int m_pendingFittingClientSizeFlags;
+#endif // __WXGTK3__
+
 protected:
     // give hints to the Window Manager for how the size
     // of the TLW can be changed by dragging
diff --git a/include/wx/window.h b/include/wx/window.h
index ece8b65451..4bc21b75b9 100644
--- a/include/wx/window.h
+++ b/include/wx/window.h
@@ -139,6 +139,13 @@ enum
     wxSEND_EVENT_POST = 1
 };
 
+// Flags for WXSetInitialFittingClientSize().
+enum
+{
+    wxSIZE_SET_CURRENT = 0x0001, // Set the current size.
+    wxSIZE_SET_MIN     = 0x0002  // Set the size as the minimum allowed size.
+};
+
 // ----------------------------------------------------------------------------
 // (pseudo)template list classes
 // ----------------------------------------------------------------------------
@@ -1541,6 +1548,13 @@ public:
     // window is part of a composite control.
     bool WXSendContextMenuEvent(const wxPoint& posInScreenCoords);
 
+    // This internal function needs to be called to set the fitting client size
+    // (i.e. the minimum size determined by the window sizer) when the size
+    // that we really need to use is not known until the window is actually
+    // shown, as is the case for TLWs with recent GTK versions, as it will
+    // update the size again when it does become known, if necessary.
+    virtual void WXSetInitialFittingClientSize(int flags);
+
         // get the handle of the window for the underlying window system: this
         // is only used for wxWin itself or for user code which wants to call
         // platform-specific APIs
diff --git a/src/common/sizer.cpp b/src/common/sizer.cpp
index 110a5d69c3..127a557ed6 100644
--- a/src/common/sizer.cpp
+++ b/src/common/sizer.cpp
@@ -999,31 +999,12 @@ wxSize wxSizer::ComputeFittingWindowSize(wxWindow *window)
     return window->ClientToWindowSize(ComputeFittingClientSize(window));
 }
 
-#ifdef __WXGTK3__
-static void FitOnShow(wxShowEvent& event)
-{
-    wxWindow* win = static_cast<wxWindow*>(event.GetEventObject());
-    wxSizer* sizer = win->GetSizer();
-    if (sizer)
-        sizer->Fit(win);
-    win->Unbind(wxEVT_SHOW, FitOnShow);
-}
-#endif
-
 wxSize wxSizer::Fit( wxWindow *window )
 {
     wxCHECK_MSG( window, wxDefaultSize, "window can't be NULL" );
 
-#ifdef __WXGTK3__
-    // GTK3 updates cached style information before showing a TLW,
-    // which may affect best size calculations, so add a handler to
-    // redo the calculations at that time
-    if (!window->IsShown() && window->IsTopLevel())
-        window->Bind(wxEVT_SHOW, FitOnShow);
-#endif
-
     // set client size
-    window->SetClientSize(ComputeFittingClientSize(window));
+    window->WXSetInitialFittingClientSize(wxSIZE_SET_CURRENT);
 
     // return entire size
     return window->GetSize();
@@ -1059,38 +1040,11 @@ void wxSizer::Layout()
     RepositionChildren(minSize);
 }
 
-#ifdef __WXGTK3__
-static void SetSizeHintsOnShow(wxShowEvent& event)
-{
-    wxWindow* win = static_cast<wxWindow*>(event.GetEventObject());
-    wxSizer* sizer = win->GetSizer();
-    if (sizer)
-        sizer->SetSizeHints(win);
-    win->Unbind(wxEVT_SHOW, SetSizeHintsOnShow);
-}
-#endif
-
 void wxSizer::SetSizeHints( wxWindow *window )
 {
     // Preserve the window's max size hints, but set the
     // lower bound according to the sizer calculations.
-
-    // This is equivalent to calling Fit(), except that we need to set
-    // the size hints _in between_ the two steps performed by Fit
-    // (1. ComputeFittingClientSize, 2. SetClientSize). That's because
-    // otherwise SetClientSize() could have no effect if there already are
-    // size hints in effect that forbid requested client size.
-
-#ifdef __WXGTK3__
-    // see comment in Fit()
-    if (!window->IsShown() && window->IsTopLevel())
-        window->Bind(wxEVT_SHOW, SetSizeHintsOnShow);
-#endif
-
-    const wxSize clientSize = ComputeFittingClientSize(window);
-
-    window->SetMinClientSize(clientSize);
-    window->SetClientSize(clientSize);
+    window->WXSetInitialFittingClientSize(wxSIZE_SET_CURRENT | wxSIZE_SET_MIN);
 }
 
 #if WXWIN_COMPATIBILITY_2_8
diff --git a/src/common/wincmn.cpp b/src/common/wincmn.cpp
index cad8c190bf..c43f6f813d 100644
--- a/src/common/wincmn.cpp
+++ b/src/common/wincmn.cpp
@@ -1002,6 +1002,25 @@ wxSize wxWindowBase::WindowToClientSize(const wxSize& size) const
                   size.y == -1 ? -1 : size.y - diff.y);
 }
 
+void wxWindowBase::WXSetInitialFittingClientSize(int flags)
+{
+    wxSizer* const sizer = GetSizer();
+    if ( !sizer )
+        return;
+
+    const wxSize
+        size = sizer->ComputeFittingClientSize(static_cast<wxWindow *>(this));
+
+    // It is important to set the min client size before changing the size
+    // itself as the existing size hints could prevent SetClientSize() from
+    // working otherwise.
+    if ( flags & wxSIZE_SET_MIN )
+        SetMinClientSize(size);
+
+    if ( flags & wxSIZE_SET_CURRENT )
+        SetClientSize(size);
+}
+
 void wxWindowBase::SetWindowVariant( wxWindowVariant variant )
 {
     if ( m_windowVariant != variant )
diff --git a/src/gtk/toplevel.cpp b/src/gtk/toplevel.cpp
index 113da04eaf..e68cf9de0d 100644
--- a/src/gtk/toplevel.cpp
+++ b/src/gtk/toplevel.cpp
@@ -612,6 +612,10 @@ void wxTopLevelWindowGTK::Init()
     m_incWidth = m_incHeight = 0;
 
     m_urgency_hint = -2;
+
+#ifdef __WXGTK3__
+    m_pendingFittingClientSizeFlags = 0;
+#endif // __WXGTK3__
 }
 
 bool wxTopLevelWindowGTK::Create( wxWindow *parent,
@@ -1161,6 +1165,12 @@ bool wxTopLevelWindowGTK::Show( bool show )
     bool change = base_type::Show(show);
 
 #ifdef __WXGTK3__
+    if (change && show)
+    {
+        // We may need to redo it after showing the window.
+        GTKUpdateClientSizeIfNecessary();
+    }
+
     if (m_needSizeEvent)
     {
         m_needSizeEvent = false;
@@ -1525,8 +1535,41 @@ void wxTopLevelWindowGTK::GTKDoAfterShow()
     wxShowEvent showEvent(GetId(), true);
     showEvent.SetEventObject(this);
     HandleWindowEvent(showEvent);
+
+#ifdef __WXGTK3__
+    // Set the client size again if necessary, we should be able to do it
+    // correctly by now as the style cache should be up to date.
+    GTKUpdateClientSizeIfNecessary();
+#endif // __WXGTK3__
 }
 
+#ifdef __WXGTK3__
+
+void wxTopLevelWindowGTK::GTKUpdateClientSizeIfNecessary()
+{
+    if ( m_pendingFittingClientSizeFlags )
+    {
+        WXSetInitialFittingClientSize(m_pendingFittingClientSizeFlags);
+
+        m_pendingFittingClientSizeFlags = 0;
+    }
+}
+
+void wxTopLevelWindowGTK::WXSetInitialFittingClientSize(int flags)
+{
+    // In any case, update the size immediately.
+    wxTopLevelWindowBase::WXSetInitialFittingClientSize(flags);
+
+    // But if we're not shown yet, the fitting size may be wrong because GTK
+    // style cache hasn't been updated yet and we need to do it again when the
+    // window becomes visible as we can be sure that by then we'll be able to
+    // compute the best size correctly.
+    if ( !IsShown() )
+        m_pendingFittingClientSizeFlags = flags;
+}
+
+#endif // __WXGTK3__
+
 // ----------------------------------------------------------------------------
 // frame title/icon
 // ----------------------------------------------------------------------------