diff --git a/Upsilon/Binder/Binder.cs b/Upsilon/Binder/Binder.cs
index 90f6109..02e2a20 100644
--- a/Upsilon/Binder/Binder.cs
+++ b/Upsilon/Binder/Binder.cs
@@ -804,8 +804,12 @@ namespace Upsilon.Binder
                 {
                     var variable = (BoundVariableExpression)indexable.Identifier;
                     var index = (BoundLiteralExpression)indexable.Index;
-                    ((TableVariableSymbol)variable.Variable.VariableSymbol).Variables.Add(index.Value.ToString(),
-                        new VariableSymbol(index.Value.ToString(), value.Type, false));
+                    var variableSymbol = variable.Variable.VariableSymbol;
+                    if (variableSymbol is TableVariableSymbol tableVariableSymbol)
+                    {
+                        tableVariableSymbol.Variables.Add(index.Value.ToString(),
+                            new VariableSymbol(index.Value.ToString(), value.Type, false));
+                    }
                 }
                 indexableExpression = indexable;
             }