diff --git a/code/ndarray.h b/code/ndarray.h
index 77826b3..c7fce67 100644
--- a/code/ndarray.h
+++ b/code/ndarray.h
@@ -24,7 +24,7 @@
 #define FLOAT_TYPECODE 'd'
 #endif
 
-const mp_obj_type_t ulab_ndarray_type;
+extern const mp_obj_type_t ulab_ndarray_type;
 
 enum NDARRAY_TYPE {
     NDARRAY_UINT8 = 'B',
diff --git a/code/ulab.c b/code/ulab.c
index 4cb31b0..60b227a 100644
--- a/code/ulab.c
+++ b/code/ulab.c
@@ -24,7 +24,7 @@
 #include "fft.h"
 #include "numerical.h"
 
-#define ULAB_VERSION 0.262
+#define ULAB_VERSION 0.263
 
 typedef struct _mp_obj_float_t {
     mp_obj_base_t base;
diff --git a/docs/ulab-change-log.md b/docs/ulab-change-log.md
index 87821be..0db085e 100644
--- a/docs/ulab-change-log.md
+++ b/docs/ulab-change-log.md
@@ -1,4 +1,10 @@
 
+Tue, 31 Dec 2019
+
+version 0.263
+
+    changed declaration of ulab_ndarray_type to extern
+
 Fri, 29 Nov 2019
 
 version 0.262
diff --git a/docs/ulab.ipynb b/docs/ulab.ipynb
index 196a0d5..2f49781 100644
--- a/docs/ulab.ipynb
+++ b/docs/ulab.ipynb
@@ -65,11 +65,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 1,
    "metadata": {
     "ExecuteTime": {
-     "end_time": "2019-11-28T18:01:44.329018Z",
-     "start_time": "2019-11-28T18:01:44.325091Z"
+     "end_time": "2019-12-31T09:52:14.092819Z",
+     "start_time": "2019-12-31T09:52:14.007217Z"
     }
    },
    "outputs": [
@@ -77,7 +77,6 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "[Errno 2] No such file or directory: '../../micropython/ports/unix/'\n",
       "/home/v923z/sandbox/micropython/v1.11/micropython/ports/unix\n"
      ]
     }
@@ -88,11 +87,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 2,
    "metadata": {
     "ExecuteTime": {
-     "end_time": "2019-11-28T18:01:47.359162Z",
-     "start_time": "2019-11-28T18:01:47.355619Z"
+     "end_time": "2019-12-31T09:52:18.816294Z",
+     "start_time": "2019-12-31T09:52:18.807776Z"
     }
    },
    "outputs": [],
@@ -135,11 +134,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 3,
    "metadata": {
     "ExecuteTime": {
-     "end_time": "2019-11-28T18:01:52.242940Z",
-     "start_time": "2019-11-28T18:01:52.195351Z"
+     "end_time": "2019-12-31T09:52:27.483535Z",
+     "start_time": "2019-12-31T09:52:27.465359Z"
     }
    },
    "outputs": [],
@@ -326,11 +325,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 4,
    "metadata": {
     "ExecuteTime": {
-     "end_time": "2019-11-28T18:01:58.976516Z",
-     "start_time": "2019-11-28T18:01:58.968120Z"
+     "end_time": "2019-12-31T09:52:40.846795Z",
+     "start_time": "2019-12-31T09:52:40.839287Z"
     }
    },
    "outputs": [],
@@ -3142,11 +3141,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 373,
+   "execution_count": 5,
    "metadata": {
     "ExecuteTime": {
-     "end_time": "2019-11-01T13:05:40.505260Z",
-     "start_time": "2019-11-01T13:05:40.499409Z"
+     "end_time": "2019-12-31T09:53:29.928666Z",
+     "start_time": "2019-12-31T09:53:29.922521Z"
     }
    },
    "outputs": [
@@ -3154,7 +3153,7 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "written 4891 bytes to ndarray.h\n"
+      "written 4898 bytes to ndarray.h\n"
      ]
     }
    ],
@@ -3177,7 +3176,7 @@
     "#define FLOAT_TYPECODE 'd'\n",
     "#endif\n",
     "\n",
-    "const mp_obj_type_t ulab_ndarray_type;\n",
+    "extern const mp_obj_type_t ulab_ndarray_type;\n",
     "\n",
     "enum NDARRAY_TYPE {\n",
     "    NDARRAY_UINT8 = 'B',\n",
@@ -7843,11 +7842,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 34,
+   "execution_count": 9,
    "metadata": {
     "ExecuteTime": {
-     "end_time": "2019-11-29T07:00:45.792518Z",
-     "start_time": "2019-11-29T07:00:45.787301Z"
+     "end_time": "2019-12-31T09:55:06.807196Z",
+     "start_time": "2019-12-31T09:55:06.802089Z"
     }
    },
    "outputs": [
@@ -7878,7 +7877,7 @@
     "#include \"fft.h\"\n",
     "#include \"numerical.h\"\n",
     "\n",
-    "#define ULAB_VERSION 0.262\n",
+    "#define ULAB_VERSION 0.263\n",
     "\n",
     "typedef struct _mp_obj_float_t {\n",
     "    mp_obj_base_t base;\n",
@@ -8107,11 +8106,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 6,
    "metadata": {
     "ExecuteTime": {
-     "end_time": "2019-11-28T18:02:23.457395Z",
-     "start_time": "2019-11-28T18:02:23.452052Z"
+     "end_time": "2019-12-31T09:53:43.473191Z",
+     "start_time": "2019-12-31T09:53:43.465796Z"
     }
    },
    "outputs": [
@@ -8129,11 +8128,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 30,
+   "execution_count": 7,
    "metadata": {
     "ExecuteTime": {
-     "end_time": "2019-11-29T06:59:01.155825Z",
-     "start_time": "2019-11-29T06:59:00.779150Z"
+     "end_time": "2019-12-31T09:53:49.156789Z",
+     "start_time": "2019-12-31T09:53:47.627853Z"
     }
    },
    "outputs": [
@@ -8157,8 +8156,8 @@
    "execution_count": null,
    "metadata": {
     "ExecuteTime": {
-     "end_time": "2019-11-29T06:59:30.206401Z",
-     "start_time": "2019-11-29T06:59:03.404517Z"
+     "end_time": "2019-12-31T09:54:21.865505Z",
+     "start_time": "2019-12-31T09:53:51.711216Z"
     },
     "scrolled": false
    },
@@ -8220,11 +8219,11 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 35,
+   "execution_count": 10,
    "metadata": {
     "ExecuteTime": {
-     "end_time": "2019-11-29T07:01:25.832268Z",
-     "start_time": "2019-11-29T07:01:25.825600Z"
+     "end_time": "2019-12-31T09:56:18.097171Z",
+     "start_time": "2019-12-31T09:56:18.091019Z"
     }
    },
    "outputs": [
@@ -8239,6 +8238,12 @@
    "source": [
     "%%writefile ../../../ulab/docs/ulab-change-log.md\n",
     "\n",
+    "Tue, 31 Dec 2019\n",
+    "\n",
+    "version 0.263\n",
+    "\n",
+    "    changed declaration of ulab_ndarray_type to extern\n",
+    "\n",
     "Fri, 29 Nov 2019\n",
     "\n",
     "version 0.262\n",