diff --git a/src/osx/cocoa/dataview.mm b/src/osx/cocoa/dataview.mm
index 37c82e49a2..ab274191cc 100644
--- a/src/osx/cocoa/dataview.mm
+++ b/src/osx/cocoa/dataview.mm
@@ -1111,6 +1111,20 @@ outlineView:(NSOutlineView*)outlineView
     return cellFrame;
 }
 
+-(NSRect)expansionFrameWithFrame:(NSRect)cellFrame
+    inView:(NSView*)view
+{
+    // We override the default behaviour to avoid showing nonsensical tooltips
+    // for the custom cells: if we don't do this, NSTextFieldCell would show a
+    // tooltip with the debug representation of wxCustomRendererObject which is
+    // not very useful.
+    //
+    // Note: override outlineView:toolTipForCell:rect:tableColumn:item:mouseLocation:
+    // in NSOutlineViewDelegate if we ever want to support per-cell tooltips
+    // instead of just suppressing them.
+    return NSZeroRect;
+}
+
 @end
 
 // ============================================================================