diff --git a/Expr.g.cs b/Expr.g.cs
index 3414526..b2c5169 100644
--- a/Expr.g.cs
+++ b/Expr.g.cs
@@ -3,7 +3,7 @@
 // DO NOT EDIT.                                           //
 ////////////////////////////////////////////////////////////
 
-using System;
+#nullable enable
 
 namespace Finn.AST;
 
diff --git a/Parser.cs b/Parser.cs
index 2a2dd86..a63ce43 100644
--- a/Parser.cs
+++ b/Parser.cs
@@ -199,7 +199,7 @@ class Parser
 		if (match(TokenType.At))
 		{
 			Token literal = consume(TokenType.String, "Expect string literal after '@'.");
-			return new((string)(literal.literal ?? ""), true);
+			return new((string)(literal.literal!), true);
 		}
 		return null;
 	}
@@ -254,7 +254,8 @@ class Parser
 	{
 		if (match(TokenType.Number, TokenType.String))
 		{
-			return new Literal { Value = previous().literal };
+			object literal = previous().literal!;
+			return new Literal { Value = previous().literal! };
 		}
 
 		var ident = name();
diff --git a/ast_classes.fsx b/ast_classes.fsx
index 0b689f6..abe7d3d 100644
--- a/ast_classes.fsx
+++ b/ast_classes.fsx
@@ -76,7 +76,7 @@ let renderAST outputDir baseName types =
 // DO NOT EDIT.                                           //
 ////////////////////////////////////////////////////////////
 
-using System;
+#nullable enable
 
 namespace Finn.AST;