diff --git a/Src/Parser/ParseResults.cs b/Src/Parser/ParseResults.cs
index da45316..f981616 100644
--- a/Src/Parser/ParseResults.cs
+++ b/Src/Parser/ParseResults.cs
@@ -35,7 +35,7 @@ public abstract class BoolLiteral<TRes, TEnv> : Literal<TRes, TEnv> {
   }
 
   public abstract class StringLiteral<TRes, TEnv> : Literal<TRes, TEnv> {
-    public string Value { get; set; }
+    public string? Value { get; set; }
   }
 
   public abstract class Symbol<TRes, TEnv>: IEvaluatable<TRes, TEnv> {
diff --git a/Src/Runtime/EvaluationNodes.cs b/Src/Runtime/EvaluationNodes.cs
index 9f7d186..d732363 100644
--- a/Src/Runtime/EvaluationNodes.cs
+++ b/Src/Runtime/EvaluationNodes.cs
@@ -33,7 +33,7 @@ public EvalBoolLit(bool b) {
 
   public class EvalStringLit: StringLiteral<Value, Environment> {
     public override Value Evaluate(Environment env) {
-      return new LiteralValue<string>(Value);
+      return new LiteralValue<string>(Value??"");
     }
 
     public EvalStringLit(string s) {