diff --git a/src/kiss/Macros.hx b/src/kiss/Macros.hx
index da8c5b0..6826012 100644
--- a/src/kiss/Macros.hx
+++ b/src/kiss/Macros.hx
@@ -176,9 +176,10 @@ class Macros {
         macros["#if"] = (wholeExp:ReaderExp, exps:Array<ReaderExp>, k) -> {
             wholeExp.checkNumArgs(2, 3, '(#if [cond] [then] [?else])');
 
+            var b = wholeExp.expBuilder();
             var conditionExp = exps.shift();
             var thenExp = exps.shift();
-            var elseExp = if (exps.length > 0) exps.shift(); else null;
+            var elseExp = if (exps.length > 0) exps.shift(); else b.symbol("null");
 
             var parser = new Parser();
             var conditionInterp = new KissInterp(true);
@@ -198,7 +199,7 @@ class Macros {
             }
         };
 
-        function bodyIf(formName:String, negated:Bool, wholeExp:ReaderExp, args:Array<ReaderExp>, k) {
+        function bodyIf(formName:String, underlyingIf:String, negated:Bool, wholeExp:ReaderExp, args:Array<ReaderExp>, k) {
             wholeExp.checkNumArgs(2, null, '($formName [condition] [body...])');
             var b = wholeExp.expBuilder();
             var condition = if (negated) {
@@ -209,13 +210,15 @@ class Macros {
             } else {
                 args[0];
             }
-            return b.call(b.symbol("if"), [
+            return b.call(b.symbol(underlyingIf), [
                 condition,
                 b.begin(args.slice(1))
             ]);
         }
-        macros["when"] = bodyIf.bind("when", false);
-        macros["unless"] = bodyIf.bind("unless", true);
+        macros["when"] = bodyIf.bind("when", "if", false);
+        macros["unless"] = bodyIf.bind("unless", "if", true);
+        macros["#when"] = bodyIf.bind("#when", "#if", false);
+        macros["#unless"] = bodyIf.bind("#unless", "#if", true);
 
         macros["cond"] = cond;
 
diff --git a/src/test/cases/ConditionalCompilationTestCase.hx b/src/test/cases/ConditionalCompilationTestCase.hx
index a7d9c11..6f7306b 100644
--- a/src/test/cases/ConditionalCompilationTestCase.hx
+++ b/src/test/cases/ConditionalCompilationTestCase.hx
@@ -17,4 +17,20 @@ class ConditionalCompilationTestCase extends Test {
         Assert.isTrue(runningInPyOrJs);
         #end
     }
+
+    function testWhen() {
+        #if interp
+        Assert.equals(6, number());
+        #else
+        Assert.equals(5, number());
+        #end
+    }
+
+    function testUnless() {
+        #if !interp
+        Assert.equals(9, number2());
+        #else
+        Assert.equals(12, number2());
+        #end
+    }
 }
diff --git a/src/test/cases/ConditionalCompilationTestCase.kiss b/src/test/cases/ConditionalCompilationTestCase.kiss
index 8564fa2..9530d76 100644
--- a/src/test/cases/ConditionalCompilationTestCase.kiss
+++ b/src/test/cases/ConditionalCompilationTestCase.kiss
@@ -1,3 +1,16 @@
 (defvar runningInHaxe (#if interp true false))
 (defvar runningInPyOrJs (#if (or py js) true false))
 
+(defun number []
+    (let [&mut num 5]
+        (#when interp
+            (+= num 5)
+            (-= num 4))
+        num))
+
+(defun number2 []
+    (let [&mut num 12]
+        (#unless interp
+            (+= num 5)
+            (-= num 8))
+        num))
\ No newline at end of file