diff --git a/Shell/AST.cpp b/Shell/AST.cpp
index 69e80ee612..d337581631 100644
--- a/Shell/AST.cpp
+++ b/Shell/AST.cpp
@@ -226,7 +226,7 @@ RefPtr<Value> ListConcatenate::run(RefPtr<Shell> shell)
 
     for (auto& element : m_list) {
         if (!result) {
-            result = create<ListValue>({ element->run(shell)->resolve_without_cast(shell).release_nonnull() });
+            result = create<ListValue>({ element->run(shell)->resolve_without_cast(shell) });
             continue;
         }
         auto element_value = element->run(shell)->resolve_without_cast(shell);
@@ -248,7 +248,7 @@ RefPtr<Value> ListConcatenate::run(RefPtr<Shell> shell)
                     values.append(create<StringValue>(result));
             }
 
-            values.append(element_value.release_nonnull());
+            values.append(element_value);
 
             result = create<ListValue>(move(values));
         }
@@ -1904,11 +1904,11 @@ Vector<String> ListValue::resolve_as_list(RefPtr<Shell> shell)
     return values;
 }
 
-RefPtr<Value> ListValue::resolve_without_cast(RefPtr<Shell> shell)
+NonnullRefPtr<Value> ListValue::resolve_without_cast(RefPtr<Shell> shell)
 {
     NonnullRefPtrVector<Value> values;
     for (auto& value : m_contained_values)
-        values.append(value.resolve_without_cast(shell).release_nonnull());
+        values.append(value.resolve_without_cast(shell));
 
     return create<ListValue>(move(values));
 }
@@ -1992,13 +1992,11 @@ Vector<String> SimpleVariableValue::resolve_as_list(RefPtr<Shell> shell)
     return res;
 }
 
-RefPtr<Value> SimpleVariableValue::resolve_without_cast(RefPtr<Shell> shell)
+NonnullRefPtr<Value> SimpleVariableValue::resolve_without_cast(RefPtr<Shell> shell)
 {
-
     if (auto value = shell->lookup_local_variable(m_name))
-        return value;
-
-    return this;
+        return value.release_nonnull();
+    return *this;
 }
 
 SpecialVariableValue::~SpecialVariableValue()
diff --git a/Shell/AST.h b/Shell/AST.h
index 546c9882a4..13d97c725d 100644
--- a/Shell/AST.h
+++ b/Shell/AST.h
@@ -168,7 +168,7 @@ class Value : public RefCounted<Value> {
 public:
     virtual Vector<String> resolve_as_list(RefPtr<Shell>) = 0;
     virtual Vector<Command> resolve_as_commands(RefPtr<Shell>);
-    virtual RefPtr<Value> resolve_without_cast(RefPtr<Shell>) { return this; }
+    virtual NonnullRefPtr<Value> resolve_without_cast(RefPtr<Shell>) { return *this; }
     virtual ~Value();
     virtual bool is_command() const { return false; }
     virtual bool is_glob() const { return false; }
@@ -233,7 +233,7 @@ private:
 class ListValue final : public Value {
 public:
     virtual Vector<String> resolve_as_list(RefPtr<Shell>) override;
-    virtual RefPtr<Value> resolve_without_cast(RefPtr<Shell>) override;
+    virtual NonnullRefPtr<Value> resolve_without_cast(RefPtr<Shell>) override;
     virtual ~ListValue();
     virtual bool is_list() const override { return true; }
     virtual bool is_list_without_resolution() const override { return true; }
@@ -286,7 +286,7 @@ private:
 class SimpleVariableValue final : public Value {
 public:
     virtual Vector<String> resolve_as_list(RefPtr<Shell>) override;
-    RefPtr<Value> resolve_without_cast(RefPtr<Shell>) override;
+    virtual NonnullRefPtr<Value> resolve_without_cast(RefPtr<Shell>) override;
     virtual ~SimpleVariableValue();
     SimpleVariableValue(String name)
         : m_name(move(name))