diff --git a/src/common/combocmn.cpp b/src/common/combocmn.cpp
index 9030ff8f4a..e3933cc65f 100644
--- a/src/common/combocmn.cpp
+++ b/src/common/combocmn.cpp
@@ -1354,9 +1354,11 @@ void wxComboCtrlBase::PositionTextCtrl( int textCtrlXAdjust, int textCtrlYAdjust
     else
     {
         // If it has border, have textctrl fill the entire text field.
+        int w = m_tcArea.width - m_widthCustomPaint;
+        if (w < 0) w = 0;
         m_text->SetSize( m_tcArea.x + m_widthCustomPaint,
                          m_tcArea.y,
-                         m_tcArea.width - m_widthCustomPaint,
+                         w,
                          m_tcArea.height );
     }
 }
diff --git a/src/gtk/collpane.cpp b/src/gtk/collpane.cpp
index ac2b928d80..386a031b9e 100644
--- a/src/gtk/collpane.cpp
+++ b/src/gtk/collpane.cpp
@@ -271,7 +271,9 @@ void wxCollapsiblePane::OnSize(wxSizeEvent &ev)
 
     // here we need to resize the pane window otherwise, even if the GtkExpander container
     // is expanded or shrunk, the pane window won't be updated!
-    m_pPane->SetSize(ev.GetSize().x, ev.GetSize().y - m_szCollapsed.y);
+    int w = ev.GetSize().y - m_szCollapsed.y;
+    if (w < 0) w = 0;
+    m_pPane->SetSize(ev.GetSize().x, w);
 
     // we need to explicitly call m_pPane->Layout() or else it won't correctly relayout
     // (even if SetAutoLayout(true) has been called on it!)