diff --git a/notebooks/chapter06_viz/06_vispy.ipynb b/notebooks/chapter06_viz/06_vispy.ipynb
index 6a986c9..ad4529d 100644
--- a/notebooks/chapter06_viz/06_vispy.ipynb
+++ b/notebooks/chapter06_viz/06_vispy.ipynb
@@ -44,7 +44,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 1,
    "metadata": {
     "collapsed": false
    },
@@ -64,7 +64,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "metadata": {
     "collapsed": false
    },
@@ -82,7 +82,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 3,
    "metadata": {
     "collapsed": false
    },
@@ -106,7 +106,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 4,
    "metadata": {
     "collapsed": false
    },
@@ -129,7 +129,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 5,
    "metadata": {
     "collapsed": false
    },
@@ -147,15 +147,15 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 8,
    "metadata": {
     "collapsed": false
    },
    "outputs": [],
    "source": [
     "program['a_position'] = np.c_[\n",
-    "        np.linspace(-1.0, +1.0, 1000),\n",
-    "        np.random.uniform(-0.5, +0.5, 1000)]"
+    "        np.linspace(-1.0, +1.0, 1000).astype(np.float32),\n",
+    "        np.random.uniform(-0.5, +0.5, 1000).astype(np.float32)]"
    ]
   },
   {
@@ -167,7 +167,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 9,
    "metadata": {
     "collapsed": false
    },
@@ -187,7 +187,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 10,
    "metadata": {
     "collapsed": false
    },
@@ -208,7 +208,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 11,
    "metadata": {
     "collapsed": false
    },
@@ -244,7 +244,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.4.2"
+   "version": "3.4.1"
   }
  },
  "nbformat": 4,