diff --git a/sentences/VHW.js b/sentences/VHW.js
index e6c0f0f..fcc06f2 100644
--- a/sentences/VHW.js
+++ b/sentences/VHW.js
@@ -19,8 +19,9 @@ module.exports = function (app) {
       'navigation.speedThroughWater'
     ],
     f: function vhw (headingTrue, magneticVariation, speedThroughWater) {
-      if (headingTrue !== null && magneticVariation !== null) {
-        var headingMagnetic = headingTrue + magneticVariation
+      var headingMagnetic
+      if (headingTrue && magneticVariation) {
+        headingMagnetic = headingTrue + magneticVariation
         if (headingMagnetic > Math.PI * 2) {
           headingMagnetic -= Math.PI * 2
         }