diff --git a/src/inc/intervals.php b/src/inc/intervals.php
index 98061e9..33c4fc7 100644
--- a/src/inc/intervals.php
+++ b/src/inc/intervals.php
@@ -46,6 +46,8 @@
 
   // Return measure of the intersection
   public static function measureIntersection($a, $b) {
-    return self::measure(self::intersect($a, $b));
+    $intersection = self::intersect($a, $b);
+    if ($intersection === false) return 0;
+    return self::measure($intersection);
   }
 }