diff --git a/src/object.h b/src/object.h
index df7b8e4..ff4e220 100644
--- a/src/object.h
+++ b/src/object.h
@@ -40,7 +40,8 @@ enum errorCode {
     NOT_A_LIST,
     SCRIPT_NOT_FOUND,
     NO_CLONE_SPECIFIED,
-    CAN_ONLY_EVAL_STRINGS
+    CAN_ONLY_EVAL_STRINGS,
+    INDEX_PAST_END,
 };
 
 #define MALLOC_FLAG 64
diff --git a/src/pebblisp.c b/src/pebblisp.c
index 77e029b..55cd717 100644
--- a/src/pebblisp.c
+++ b/src/pebblisp.c
@@ -462,7 +462,12 @@ Object prepend(Object list, Object newElement, struct Environment *env)
 
 Object at(Object index, Object list, struct Environment *env)
 {
-    return cloneObject(*itemAt(&list, index.number));
+    const Object *found = itemAt(&list, index.number);
+    if(found) {
+        return cloneObject(*found);
+    } else {
+        return errorObject(INDEX_PAST_END);
+    }
 }
 
 Object rest(Object list, Object ignore, struct Environment *env)