diff --git a/chapter_preliminaries/ndarray.ipynb b/chapter_preliminaries/ndarray.ipynb
index eee3aff0..f2c15392 100644
--- a/chapter_preliminaries/ndarray.ipynb
+++ b/chapter_preliminaries/ndarray.ipynb
@@ -718,7 +718,7 @@
    },
    "outputs": [],
    "source": [
-    "x.get(\":-1\");"
+    "x.get(\"-1\");"
    ]
   },
   {
@@ -872,7 +872,7 @@
    "mimetype": "text/x-java-source",
    "name": "Java",
    "pygments_lexer": "java",
-   "version": "14.0.2+12"
+   "version": "18.0.1+10-24"
   }
  },
  "nbformat": 4,