diff --git a/OGP1718-Worms/src/worms/model/Worm.java b/OGP1718-Worms/src/worms/model/Worm.java
index 378eb35..a2ff2de 100644
--- a/OGP1718-Worms/src/worms/model/Worm.java
+++ b/OGP1718-Worms/src/worms/model/Worm.java
@@ -160,6 +160,15 @@ public class Worm {
         this.location = location;
     }
 
+    /**
+     * check whether the given location is a valid location for the worm
+     * 
+     * @param location
+     * 		  the location to check
+     * @return True if and only if the location is not equal to null and the coordinates of
+     * 		   the worm are numbers
+     * 		   |result == (location != null) && (!Double.isNaN(location.item1)) && (!Double.isNaN(location.item2))
+     */
     private boolean isValidLocation(Tuple<Double, Double>location) {
         return location != null && !Double.isNaN(location.item1) && !Double.isNaN(location.item2);
     }