diff --git a/src/minicharts/d3-tip.js b/src/minicharts/d3-tip.js
index 719749e4950..175c8978b05 100644
--- a/src/minicharts/d3-tip.js
+++ b/src/minicharts/d3-tip.js
@@ -66,8 +66,8 @@
       }
       coords = direction_callbacks.get(dir).apply(this);
       nodel.classed(dir, true).style({
-        top: (coords.top + poffset[0]) + scrollTop + 'px',
-        left: (coords.left + poffset[1]) + scrollLeft + 'px'
+        top: (coords.top + poffset[0] + scrollTop).toString() + 'px',
+        left: (coords.left + poffset[1] + scrollLeft).toString() + 'px'
       });
 
       return tip;