diff --git a/build.json b/build.json
index d25024de..624d8aa5 100644
--- a/build.json
+++ b/build.json
@@ -1,7 +1,7 @@
 {
   "variable": {
     "PYTHON_VERSION": {
-      "default": "3.9.4"
+      "default": "3.9.13"
     },
     "AIIDA_VERSION": {
       "default": "2.1.2"
diff --git a/stack/base/Dockerfile b/stack/base/Dockerfile
index ea52feb5..7db2a3be 100644
--- a/stack/base/Dockerfile
+++ b/stack/base/Dockerfile
@@ -1,4 +1,4 @@
-ARG BASE=jupyter/minimal-notebook:python-3.9.13
+ARG BASE
 FROM ${BASE}
 
 LABEL maintainer="AiiDAlab Team <aiidalab@materialscloud.org>"