diff --git a/browser/base/content/tabview/modules/utils.jsm b/browser/base/content/tabview/modules/utils.jsm
index ee0318f81ab..7985eb1c0b1 100644
--- a/browser/base/content/tabview/modules/utils.jsm
+++ b/browser/base/content/tabview/modules/utils.jsm
@@ -322,6 +322,20 @@ Range.prototype = {
     return false;
   },
 
+  // ----------
+  // Function: overlaps
+  // Whether the <Range> overlaps with the given <Range> or value or not.
+  //
+  // Paramaters
+  //  - a number or <Range>
+  overlaps: function Rect_overlaps(value) {
+    if (Utils.isNumber(value))
+      return this.contains(value);
+    if (Utils.isRange(value))
+      return !(value.max < this.min || this.max < value.min);
+    return false;
+  },
+
   // ----------
   // Function: proportion
   // Maps the given value to the range [0,1], so that it returns 0 if the value is <= the min,
diff --git a/browser/base/content/tabview/trench.js b/browser/base/content/tabview/trench.js
index e4812ac814e..b08ff4fef1f 100644
--- a/browser/base/content/tabview/trench.js
+++ b/browser/base/content/tabview/trench.js
@@ -382,7 +382,7 @@ Trench.prototype = {
   ruleOverlaps: function Trench_ruleOverlaps(position, range) {
     return (this.position - this.radius < position &&
            position < this.position + this.radius &&
-           this.activeRange.contains(range));
+           this.activeRange.overlaps(range));
   },
 
   //----------