diff --git a/calcs/courseOverGroundMagnetic.js b/calcs/courseOverGroundMagnetic.js
index f79bf3b..aa8c8f3 100644
--- a/calcs/courseOverGroundMagnetic.js
+++ b/calcs/courseOverGroundMagnetic.js
@@ -15,9 +15,9 @@ module.exports = function (app, plugin) {
         magneticVariation = app.getSelfPath(
           'navigation.magneticVariation.value'
         )
-        if (_.isUndefined(magneticVariation)) {
-          return
-        }
+      }
+      if (_.isUndefined(magneticVariation) || magneticVariation === null) {
+        return
       }
       if (
         _.isUndefined(courseOverGroundTrue) ||
@@ -46,6 +46,9 @@ module.exports = function (app, plugin) {
       {
         input: [null, -0.01],
         expected: [{ path: 'navigation.courseOverGroundMagnetic', value: null }]
+      },
+      {
+        input: [0.2, null]
       }
     ]
   }
diff --git a/calcs/courseOverGroundTrue.js b/calcs/courseOverGroundTrue.js
index e520bb9..266adbb 100644
--- a/calcs/courseOverGroundTrue.js
+++ b/calcs/courseOverGroundTrue.js
@@ -15,9 +15,9 @@ module.exports = function (app, plugin) {
         magneticVariation = app.getSelfPath(
           'navigation.magneticVariation.value'
         )
-        if (_.isUndefined(magneticVariation)) {
-          return
-        }
+      }
+      if (_.isUndefined(magneticVariation) || magneticVariation === null) {
+        return
       }
       if (
         _.isUndefined(courseOverGroundMagnetic) ||
@@ -39,6 +39,9 @@ module.exports = function (app, plugin) {
       {
         input: [null, 0.01],
         expected: [{ path: 'navigation.courseOverGroundTrue', value: null }]
+      },
+      {
+        input: [0.2, null]
       }
     ]
   }
diff --git a/calcs/headingTrue.js b/calcs/headingTrue.js
index 946ebb6..9eb1972 100644
--- a/calcs/headingTrue.js
+++ b/calcs/headingTrue.js
@@ -12,9 +12,9 @@ module.exports = function (app, plugin) {
         magneticVariation = app.getSelfPath(
           'navigation.magneticVariation.value'
         )
-        if (_.isUndefined(magneticVariation)) {
-          return
-        }
+      }
+      if (_.isUndefined(magneticVariation) || magneticVariation === null) {
+        return
       }
       if (_.isUndefined(heading) || heading === null) {
         return [{ path: 'navigation.headingTrue', value: null }]
@@ -31,6 +31,9 @@ module.exports = function (app, plugin) {
       {
         input: [null, 0.01],
         expected: [{ path: 'navigation.headingTrue', value: null }]
+      },
+      {
+        input: [0.2, null]
       }
     ]
   }
diff --git a/calcs/setDrift.js b/calcs/setDrift.js
index 26a4d5a..146a5c9 100644
--- a/calcs/setDrift.js
+++ b/calcs/setDrift.js
@@ -52,7 +52,7 @@ module.exports = function (app, plugin) {
       }
 
       var setTrue = setMagnetic + magneticVariation
-      if (_.isUndefined(magneticVariation)) {
+      if (_.isUndefined(magneticVariation) || magneticVariation === null) {
         setTrue = null
       } else if (setTrue >= 2 * Math.Pi) {
         setTrue = setTrue - Math.PI * 2
@@ -65,6 +65,22 @@ module.exports = function (app, plugin) {
         { path: 'environment.current.setTrue', value: setTrue },
         { path: 'environment.current.setMagnetic', value: setMagnetic }
       ]
-    }
+    },
+    tests: [
+      {
+        input: [0.1, 0.2, 5, 4.5, null],
+        expected: [
+          { path: 'environment.current.drift', value: 0.6890664427243886 },
+          {
+            path: 'environment.current.setTrue',
+            value: null
+          },
+          {
+            path: 'environment.current.setMagnetic',
+            value: 3.0482899952302343
+          }
+        ]
+      }
+    ]
   }
 }
diff --git a/calcs/windDirectionMagnetic.js b/calcs/windDirectionMagnetic.js
index 986f737..ed7ee81 100644
--- a/calcs/windDirectionMagnetic.js
+++ b/calcs/windDirectionMagnetic.js
@@ -8,7 +8,7 @@ module.exports = function (app, plugin) {
       'navigation.magneticVariation'
     ],
     calculator: function (directionTrue, magneticVariation) {
-      if (directionTrue === null) {
+      if (directionTrue === null || magneticVariation === null) {
         return [{ path: 'environment.wind.directionMagnetic', value: null }]
       }
       var directionMagnetic = directionTrue - magneticVariation
@@ -25,6 +25,10 @@ module.exports = function (app, plugin) {
       {
         input: [null, -0.01],
         expected: [{ path: 'environment.wind.directionMagnetic', value: null }]
+      },
+      {
+        input: [0.2, null],
+        expected: [{ path: 'environment.wind.directionMagnetic', value: null }]
       }
     ]
   }