diff --git a/src/kiss/Kiss.hx b/src/kiss/Kiss.hx
index bb521d1..20f3885 100644
--- a/src/kiss/Kiss.hx
+++ b/src/kiss/Kiss.hx
@@ -186,7 +186,8 @@ class Kiss {
                 "readDirectory" => Symbol("Prelude.readDirectory"),
                 "substr" => Symbol("Prelude.substr"),
                 "isListExp" => Symbol("Prelude.isListExp"),
-                "isNull" => Symbol("Prelude.isNull")
+                "isNull" => Symbol("Prelude.isNull"),
+                "isNotNull" => Symbol("Prelude.isNotNull")
                 /* zip functions used to live here as aliases but now they are macros that also
                 apply (the Array<Array<Dynamic>>) to the result */
                 /* intersect used to live here as an alias but now it is in a macro that also
diff --git a/src/kiss/Prelude.hx b/src/kiss/Prelude.hx
index ea8033a..afcca56 100644
--- a/src/kiss/Prelude.hx
+++ b/src/kiss/Prelude.hx
@@ -431,11 +431,12 @@ class Prelude {
 
     public static var joinPath:Function = Reflect.makeVarArgs(_joinPath);
 
-    public static function isNull<T>(v:T) {
-        return switch (Type.typeof(v)) {
-            case TNull: true;
-            default: false;
-        }
+    public static function isNull<T>(v:Null<T>) {
+        return v == null;
+    }
+    
+    public static function isNotNull<T>(v:Null<T>) {
+        return v != null;
     }
 
     public static dynamic function truthy<T>(v:T) {