diff --git a/src/math/rectf.hpp b/src/math/rectf.hpp
index 80bc47829bd..cdff094b496 100644
--- a/src/math/rectf.hpp
+++ b/src/math/rectf.hpp
@@ -129,6 +129,12 @@ class Rectf
     return ((v1 - v2).norm ());
   }
 
+  Rectf grown(float border) const
+  {
+    return Rectf(p1.x - border, p1.y - border,
+                 p2.x + border, p2.y + border);
+  }
+
   // leave these two public to save the headaches of set/get functions for such
   // simple things :)