diff --git a/src/env/core.rs b/src/env/core.rs
index b36c3f7..a6d1606 100644
--- a/src/env/core.rs
+++ b/src/env/core.rs
@@ -242,6 +242,11 @@ pub(super) fn core() -> HashMap<String, Node> {
         (
             "if",
             Node::Special(|env, args| {
+                let mut args = args;
+                if args.len() == 2 {
+                    args.push(Node::Nil)
+                }
+
                 arg_count!(3, args.len());
                 let mut args = args.into_iter();
 
diff --git a/src/evaluator.rs b/src/evaluator.rs
index b79a418..fe8b79b 100644
--- a/src/evaluator.rs
+++ b/src/evaluator.rs
@@ -141,6 +141,8 @@ mod test {
     #[case("(if false true false)", "false")]
     #[case("(if 4 true false)", "true")]
     #[case("(if \"blue\" true false)", "true")]
+    #[case("(if true 3)", "3")]
+    #[case("(if false 3)", "()")]
     // Functions
     #[case("((fn* (a) a) 3)", "3")]
     #[case("((fn* (a) (+ a 2)) 1)", "3")]